diff --git a/Core/src/org/sleuthkit/autopsy/core/Bundle.properties-MERGED b/Core/src/org/sleuthkit/autopsy/core/Bundle.properties-MERGED
index c0407c965b..fce17d6606 100755
--- a/Core/src/org/sleuthkit/autopsy/core/Bundle.properties-MERGED
+++ b/Core/src/org/sleuthkit/autopsy/core/Bundle.properties-MERGED
@@ -2,6 +2,10 @@ Installer.closing.confirmationDialog.message=Ingest is running, are you sure you
 Installer.closing.confirmationDialog.title=Ingest is Running
 # {0} - exception message
 Installer.closing.messageBox.caseCloseExceptionMessage=Error closing case: {0}
+# {0} - maxMemory
+Installer_checkMemoryAvailable_maxMemExpected_desc=Maximum JVM memory: {0}, is less than the 2 GB required.  Some aspects of the application may not work as expected.
+# {0} - physicalMemory
+Installer_checkMemoryAvailable_physicalRamExpected_desc=Physical memory: {0}, is less than the 8 GB required.  Some aspects of the application may not work as expected.
 OpenIDE-Module-Display-Category=Infrastructure
 OpenIDE-Module-Long-Description=\
     This is the core Autopsy module.\n\n\
diff --git a/Core/src/org/sleuthkit/autopsy/core/Installer.java b/Core/src/org/sleuthkit/autopsy/core/Installer.java
index 24c40e9967..0cbafe987e 100644
--- a/Core/src/org/sleuthkit/autopsy/core/Installer.java
+++ b/Core/src/org/sleuthkit/autopsy/core/Installer.java
@@ -20,8 +20,10 @@ package org.sleuthkit.autopsy.core;
 
 import com.sun.jna.platform.win32.Kernel32;
 import java.awt.Cursor;
+import java.awt.GraphicsEnvironment;
 import java.io.File;
 import java.io.IOException;
+import java.lang.management.ManagementFactory;
 import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.util.ArrayList;
@@ -34,6 +36,7 @@ import java.util.logging.Level;
 import javafx.application.Platform;
 import javafx.embed.swing.JFXPanel;
 import javax.imageio.ImageIO;
+import javax.swing.JOptionPane;
 import net.sf.sevenzipjbinding.SevenZip;
 import net.sf.sevenzipjbinding.SevenZipNativeInitializationException;
 import org.apache.commons.io.FileUtils;
@@ -41,6 +44,7 @@ import org.apache.commons.lang3.StringUtils;
 import org.openide.modules.InstalledFileLocator;
 import org.openide.modules.ModuleInstall;
 import org.openide.util.NbBundle;
+import org.openide.util.NbBundle.Messages;
 import org.openide.windows.WindowManager;
 import org.sleuthkit.autopsy.actions.IngestRunningCheck;
 import org.sleuthkit.autopsy.casemodule.Case;
@@ -373,6 +377,7 @@ public class Installer extends ModuleInstall {
     @Override
     public void restored() {
         super.restored();
+        checkMemoryAvailable();
         ensurePythonModulesFolderExists();
         ensureClassifierFolderExists();
         ensureOcrLanguagePacksFolderExists();
@@ -392,6 +397,40 @@ public class Installer extends ModuleInstall {
         preloadTranslationServices();
     }
 
+    /**
+     * Checks system resources logging any potential issues.
+     */
+    @Messages({
+        "# {0} - physicalMemory",
+        "Installer_checkMemoryAvailable_physicalRamExpected_desc=Physical memory: {0}, is less than the 8 GB required.  Some aspects of the application may not work as expected.",
+        "# {0} - maxMemory",
+        "Installer_checkMemoryAvailable_maxMemExpected_desc=Maximum JVM memory: {0}, is less than the 2 GB required.  Some aspects of the application may not work as expected."
+    })
+    private void checkMemoryAvailable() {
+        try {
+            long memorySize = ((com.sun.management.OperatingSystemMXBean) ManagementFactory
+                    .getOperatingSystemMXBean()).getTotalMemorySize();
+            if (memorySize < 8_000_000_000L) {
+                String desc = Bundle.Installer_checkMemoryAvailable_physicalRamExpected_desc(
+                        FileUtils.byteCountToDisplaySize(memorySize));
+                logger.log(Level.SEVERE, desc);
+            }
+        } catch (Throwable t) {
+            logger.log(Level.SEVERE, "There was an error fetching physical memory size", t);
+        }
+
+        try {
+            long maxMemory = Runtime.getRuntime().maxMemory();
+            if (maxMemory < 2_000_000_000L) {
+                String desc = Bundle.Installer_checkMemoryAvailable_maxMemExpected_desc(
+                        FileUtils.byteCountToDisplaySize(maxMemory));
+                logger.log(Level.SEVERE, desc);
+            }
+        } catch (Throwable t) {
+            logger.log(Level.SEVERE, "There was an error fetching jvm max memory", t);
+        }
+    }
+
     /**
      * Initializes 7zip-java bindings. We are performing initialization once
      * because we encountered issues related to file locking when initialization
diff --git a/Core/src/org/sleuthkit/autopsy/progress/ModalDialogProgressIndicator.java b/Core/src/org/sleuthkit/autopsy/progress/ModalDialogProgressIndicator.java
index 31fb900c56..b3d5c6b828 100644
--- a/Core/src/org/sleuthkit/autopsy/progress/ModalDialogProgressIndicator.java
+++ b/Core/src/org/sleuthkit/autopsy/progress/ModalDialogProgressIndicator.java
@@ -263,4 +263,11 @@ public final class ModalDialogProgressIndicator implements ProgressIndicator {
         dialog.setLocationRelativeTo(parent);
         this.dialog.setVisible(true);
     }
+    
+    /**
+     * @return The GUI dialog presenting the progress.  Possibly null.
+     */
+    public Dialog getDialog() {
+        return this.dialog;
+    }
 }
diff --git a/KeywordSearch/src/org/sleuthkit/autopsy/keywordsearch/Bundle.properties-MERGED b/KeywordSearch/src/org/sleuthkit/autopsy/keywordsearch/Bundle.properties-MERGED
index 0bf48a5370..ffdaa49829 100755
--- a/KeywordSearch/src/org/sleuthkit/autopsy/keywordsearch/Bundle.properties-MERGED
+++ b/KeywordSearch/src/org/sleuthkit/autopsy/keywordsearch/Bundle.properties-MERGED
@@ -306,6 +306,14 @@ KeywordSearchModuleFactory.getIngestJobSettingsPanel.exception.msg=Expected sett
 KeywordSearchModuleFactory.createFileIngestModule.exception.msg=Expected settings argument to be instanceof KeywordSearchJobSettings
 SearchRunner.Searcher.done.err.msg=Error performing keyword search
 Server.status.failed.msg=Local Solr server did not respond to status request. This may be because the server failed to start or is taking too long to initialize.
+# {0} - indexVersion
+Server_configureSolrConnection_illegalSolrVersion=The solr version in the case: {0}, is not supported.
+# {0} - solrVersion
+# {1} - caseName
+Server_configureSolrConnection_unsupportedSolrDesc=<html><body><p style="width: 400px">This case was made with an older version of Keyword Search that is no longer supported.  You can continue without upgrading, but some Keyword Search functionality will not be usable while the case is open, and you will encounter errors.  You can also choose to upgrade the Keyword Search version for the case.  If you choose to do this, you will need to run Keyword Search with Solr indexing selected in order to use features like ad hoc search with images in the case.</p></body></html>
+Server_configureSolrConnection_unsupportedSolrDisableOpt=Continue
+Server_configureSolrConnection_unsupportedSolrTitle=Unsupported Keyword Search in Case
+Server_configureSolrConnection_unsupportedSolrUpgradeOpt=Upgrade Solr Core
 SolrConnectionCheck.HostnameOrPort=Invalid hostname and/or port number.
 SolrConnectionCheck.Hostname=Invalid hostname.
 SolrConnectionCheck.MissingHostname=Missing hostname.
diff --git a/KeywordSearch/src/org/sleuthkit/autopsy/keywordsearch/KeywordSearchJobSettings.java b/KeywordSearch/src/org/sleuthkit/autopsy/keywordsearch/KeywordSearchJobSettings.java
index 133c3b37db..f04506d76a 100644
--- a/KeywordSearch/src/org/sleuthkit/autopsy/keywordsearch/KeywordSearchJobSettings.java
+++ b/KeywordSearch/src/org/sleuthkit/autopsy/keywordsearch/KeywordSearchJobSettings.java
@@ -29,7 +29,8 @@ import org.sleuthkit.autopsy.ingest.IngestModuleIngestJobSettings;
 public final class KeywordSearchJobSettings implements IngestModuleIngestJobSettings {
 
     private static final long serialVersionUID = 1L;
-
+    private static final boolean DEFAULT_INDEX_TO_SOLR = true;
+    
     private final HashSet<String> namesOfEnabledKeywordLists;
     private HashSet<String> namesOfDisabledKeywordLists; // Added in version 1.1
 
@@ -42,7 +43,8 @@ public final class KeywordSearchJobSettings implements IngestModuleIngestJobSett
 
     private boolean ocrOnly;
     
-    private boolean indexToSolr;
+    // use object boolean so older settings missing this setting will deserialize to null.
+    private Boolean indexToSolr;
 
     /**
      * Constructs ingest job settings for the keywords search module.
@@ -202,7 +204,7 @@ public final class KeywordSearchJobSettings implements IngestModuleIngestJobSett
     }
     
     boolean isIndexToSolrEnabled() {
-        return indexToSolr;
+        return indexToSolr == null ? DEFAULT_INDEX_TO_SOLR : indexToSolr;
     }
     
     void setIndexToSolrEnabled(boolean enabled){
diff --git a/KeywordSearch/src/org/sleuthkit/autopsy/keywordsearch/Server.java b/KeywordSearch/src/org/sleuthkit/autopsy/keywordsearch/Server.java
index 9d04595f09..b918a81054 100644
--- a/KeywordSearch/src/org/sleuthkit/autopsy/keywordsearch/Server.java
+++ b/KeywordSearch/src/org/sleuthkit/autopsy/keywordsearch/Server.java
@@ -57,6 +57,7 @@ import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.stream.Collectors;
 import static java.util.stream.Collectors.toList;
+import javax.swing.JOptionPane;
 import org.apache.solr.client.solrj.SolrQuery;
 import org.apache.solr.client.solrj.SolrRequest;
 import org.apache.solr.client.solrj.SolrServerException;
@@ -82,6 +83,7 @@ import org.apache.solr.common.util.NamedList;
 import org.openide.modules.InstalledFileLocator;
 import org.openide.modules.Places;
 import org.openide.util.NbBundle;
+import org.openide.util.NbBundle.Messages;
 import org.openide.windows.WindowManager;
 import org.sleuthkit.autopsy.casemodule.Case;
 import org.sleuthkit.autopsy.casemodule.Case.CaseType;
@@ -611,18 +613,22 @@ public class Server {
         startLocalSolr(SOLR_VERSION.SOLR8);
     }
     
+    @Messages({
+        "# {0} - indexVersion",
+        "Server_configureSolrConnection_illegalSolrVersion=The solr version in the case: {0}, is not supported."
+    })
     private void configureSolrConnection(Case theCase, Index index) throws KeywordSearchModuleException, SolrServerNoPortException {
         
         try {
             if (theCase.getCaseType() == CaseType.SINGLE_USER_CASE) {
 
                 // makes sure the proper local Solr server is running
-                if (IndexFinder.getCurrentSolrVersion().equals(index.getSolrVersion())) {
-                    startLocalSolr(SOLR_VERSION.SOLR8);
-                } else {
-                    startLocalSolr(SOLR_VERSION.SOLR4);
+                if (!IndexFinder.getCurrentSolrVersion().equals(index.getSolrVersion())) {
+                    throw new KeywordSearchModuleException(Bundle.Server_configureSolrConnection_illegalSolrVersion(index.getSolrVersion()));
                 }
 
+                startLocalSolr(SOLR_VERSION.SOLR8);
+                
                 // check if the local Solr server is running
                 if (!this.isLocalSolrRunning()) {
                     logger.log(Level.SEVERE, "Local Solr server is not running"); //NON-NLS
@@ -684,8 +690,7 @@ public class Server {
         if (version == SOLR_VERSION.SOLR8) {
             localSolrFolder = InstalledFileLocator.getDefault().locate("solr", Server.class.getPackage().getName(), false); //NON-NLS
         } else {
-            // solr4
-            localSolrFolder = InstalledFileLocator.getDefault().locate("solr4", Server.class.getPackage().getName(), false); //NON-NLS
+            throw new KeywordSearchModuleException(Bundle.Server_configureSolrConnection_illegalSolrVersion(version.name()));
         }
 
         if (isLocalSolrRunning()) {
diff --git a/KeywordSearch/src/org/sleuthkit/autopsy/keywordsearch/SolrSearchService.java b/KeywordSearch/src/org/sleuthkit/autopsy/keywordsearch/SolrSearchService.java
index d9dd4d921a..8c6278b5b2 100644
--- a/KeywordSearch/src/org/sleuthkit/autopsy/keywordsearch/SolrSearchService.java
+++ b/KeywordSearch/src/org/sleuthkit/autopsy/keywordsearch/SolrSearchService.java
@@ -18,6 +18,7 @@
  */
 package org.sleuthkit.autopsy.keywordsearch;
 
+import java.awt.Component;
 import java.io.File;
 import java.io.IOException;
 import java.io.Reader;
@@ -26,18 +27,22 @@ import java.util.ArrayList;
 import java.util.List;
 import java.util.MissingResourceException;
 import java.util.logging.Level;
+import javax.swing.JOptionPane;
 import org.apache.solr.client.solrj.SolrServerException;
 import org.openide.util.NbBundle;
 import org.openide.util.lookup.ServiceProvider;
 import org.openide.util.lookup.ServiceProviders;
+import org.openide.windows.WindowManager;
 import org.sleuthkit.autopsy.appservices.AutopsyService;
 import org.sleuthkit.autopsy.casemodule.Case;
 import org.sleuthkit.autopsy.casemodule.CaseMetadata;
+import org.sleuthkit.autopsy.core.RuntimeProperties;
 import org.sleuthkit.autopsy.coreutils.FileUtil;
 import org.sleuthkit.autopsy.coreutils.Logger;
 import org.sleuthkit.autopsy.ingest.IngestManager;
 import org.sleuthkit.autopsy.keywordsearchservice.KeywordSearchService;
 import org.sleuthkit.autopsy.keywordsearchservice.KeywordSearchServiceException;
+import org.sleuthkit.autopsy.progress.ModalDialogProgressIndicator;
 import org.sleuthkit.autopsy.progress.ProgressIndicator;
 import org.sleuthkit.autopsy.textextractors.TextExtractor;
 import org.sleuthkit.autopsy.textextractors.TextExtractorFactory;
@@ -315,11 +320,25 @@ public class SolrSearchService implements KeywordSearchService, AutopsyService {
                     }
                     throw new AutopsyServiceException(Bundle.SolrSearch_unableToFindIndex_msg());
                 }
+                
+
 
                 if (context.cancelRequested()) {
                     return;
                 }
 
+                if (!IndexFinder.getCurrentSolrVersion().equals(indexToUse.getSolrVersion())) {
+                    Index prevIndex = indexToUse;
+                    indexToUse = tryUpgradeSolrVersion(context, indexToUse);
+                    if (indexToUse != prevIndex) {
+                        indexes.add(indexToUse);    
+                    }
+                }
+                
+                if (context.cancelRequested()) {
+                    return;
+                }
+                                
                 // check if schema is compatible
                 if (!indexToUse.isCompatible(IndexFinder.getCurrentSchemaVersion())) {
                     String msg = "Text index schema version " + indexToUse.getSchemaVersion() + " is not compatible with current schema";
@@ -355,6 +374,71 @@ public class SolrSearchService implements KeywordSearchService, AutopsyService {
 
         progress.progress(Bundle.SolrSearch_complete_msg(), totalNumProgressUnits);
     }
+    
+    
+    private static final long WAIT_TIME_MILLIS = 2000;
+    
+    /**
+     * Attempts to upgrade the solr version to most recent version first prompting the user.
+     * @param context The case context.
+     * @param index The current index.
+     * @return The new index.
+     * @throws org.sleuthkit.autopsy.appservices.AutopsyService.AutopsyServiceException 
+     */
+    @NbBundle.Messages({
+        "Server_configureSolrConnection_unsupportedSolrTitle=Unsupported Keyword Search in Case",
+        "# {0} - solrVersion",
+        "# {1} - caseName",
+        "Server_configureSolrConnection_unsupportedSolrDesc=<html><body><p style=\"width: 400px\">This case was made with an older version of Keyword Search that is no longer supported.  You can continue without upgrading, but some Keyword Search functionality will not be usable while the case is open, and you will encounter errors.  You can also choose to upgrade the Keyword Search version for the case.  If you choose to do this, you will need to run Keyword Search with Solr indexing selected in order to use features like ad hoc search with images in the case.</p></body></html>",
+        "Server_configureSolrConnection_unsupportedSolrDisableOpt=Continue",
+        "Server_configureSolrConnection_unsupportedSolrUpgradeOpt=Upgrade Solr Core"
+    })
+    private Index tryUpgradeSolrVersion(CaseContext context, Index index) throws AutopsyServiceException {
+        // if not, attempt to fix issue
+        if (RuntimeProperties.runningWithGUI()) {
+            Component parentComponent = WindowManager.getDefault().getMainWindow();
+            if (context.getProgressIndicator() instanceof ModalDialogProgressIndicator progInd && progInd.getDialog() != null) {
+                parentComponent = progInd.getDialog();
+
+            }
+            
+            if (context.cancelRequested()) {
+                return index;
+            }
+
+            try {
+                // progress updates occur right before this in the same window, so there is the possibility that
+                // the progress window will update just after the option pane is shown causing the option pane to
+                // not be visible or selectable.  This sleep is added to give the window enough time to finish
+                Thread.sleep(WAIT_TIME_MILLIS);
+            } catch (InterruptedException ex) {
+                // just proceed if interrupted
+            }
+            
+            if (context.cancelRequested()) {
+                return index;
+            }
+
+            int selection = JOptionPane.showOptionDialog(
+                    parentComponent,
+                    Bundle.Server_configureSolrConnection_unsupportedSolrDesc(index.getSolrVersion(), context.getCase().getDisplayName()),
+                    Bundle.Server_configureSolrConnection_unsupportedSolrTitle(),
+                    JOptionPane.YES_NO_OPTION,
+                    JOptionPane.WARNING_MESSAGE,
+                    null,
+                    new Object[]{
+                        Bundle.Server_configureSolrConnection_unsupportedSolrDisableOpt(),
+                        Bundle.Server_configureSolrConnection_unsupportedSolrUpgradeOpt()
+                    },
+                    Bundle.Server_configureSolrConnection_unsupportedSolrDisableOpt());
+
+            if (selection == 1) {
+                return IndexFinder.createLatestVersionIndex(context.getCase());
+            }
+        }
+
+        throw new AutopsyServiceException("Unsupported Keyword Search (Solr " + index.getSolrVersion() + ")");
+    }
 
     /**
      * Closes the open core.
diff --git a/Running_Linux_OSX.md b/Running_Linux_OSX.md
index c35ca091e0..529b89f127 100644
--- a/Running_Linux_OSX.md
+++ b/Running_Linux_OSX.md
@@ -1,5 +1,8 @@
 # Overview
-When installing on Debian-based Linux or macOS systems, there are three general steps: [installing prerequisites](#installing-prerequisites), [installing The Sleuth Kit](#installing-the-sleuth-kit), and [installing Autopsy](#installing-autopsy) itself.  On macOS, you will want to [setup the JNA paths](#setup-macos-jna-paths).
+For Linux systems that [support snapd](https://snapcraft.io/docs/installing-snapd), there is currently the option to install Autopsy from the [snap package](#install-autopsy-snap).  Otherwise, when installing on Debian-based Linux or macOS systems, there are three general steps: [installing prerequisites](#installing-prerequisites), [installing The Sleuth Kit](#installing-the-sleuth-kit), and [installing Autopsy](#installing-autopsy) itself.  On macOS, you will want to [setup the JNA paths](#setup-macos-jna-paths).
+
+# Install Autopsy Snap
+You can download the snap package from the [releases section](https://github.com/sleuthkit/autopsy/releases).  In order for Autopsy to run properly, snap connections will need to be properly setup, which can be done by running this script: `snap connections autopsy | sed -nE 's/^[^ ]* *([^ ]*) *- *- *$/\1/p' | xargs -I{} sudo snap connect {}`.  See the [snap README](./snap/README.md) for more information.
 
 # Installing Prerequisites
 - **Linux**: Run [`linux_macos_install_scripts/install_prereqs_ubuntu.sh`](./linux_macos_install_scripts/install_prereqs_ubuntu.sh).
diff --git a/snap/snapcraft.yaml b/snap/snapcraft.yaml
index d32596b9ee..bbbb3b9b17 100644
--- a/snap/snapcraft.yaml
+++ b/snap/snapcraft.yaml
@@ -19,10 +19,11 @@
 # yaml reference here: https://snapcraft.io/docs/snapcraft-yaml-reference
 # sample yaml files here: https://github.com/videolan/vlc/blob/master/extras/package/snap/snapcraft.yaml, https://github.com/canonical/firefox-snap/blob/stable/snapcraft.yaml
 name: autopsy
+title: Autopsy
 # more on base snaps here: https://snapcraft.io/docs/base-snaps
 # core is based on corresponding ubuntu version.  ubuntu version information can be found here: https://wiki.ubuntu.com/Releases
 base: core22
-version: 4.20.0
+version: 4.21.0
 summary: A graphical interface to The Sleuth Kit and other digital forensics tools. # 79 char long summary
 description: Autopsy is a graphical interface to The Sleuth Kit and other open source digital forensics tools.
 source-code: https://github.com/sleuthkit/autopsy/
@@ -38,7 +39,7 @@ compression: lzo
 icon: snap/gui/autopsy.png
 
 plugs:
-  system-files-autopsy:
+  system-files-dev:
     interface: system-files
     read: [/dev]
   system-files-hugepages:
@@ -88,7 +89,6 @@ apps:
       # taken from https://snapcraft.io/docs/supported-interfaces
       - audio-playback
       - block-devices
-      - browser-sandbox
       - desktop
       - desktop-launch
       - desktop-legacy
@@ -108,7 +108,7 @@ apps:
       - opengl
       - optical-drive
       - removable-media
-      - system-files-autopsy
+      - system-files-dev
       - system-files-hugepages
       - system-observe
     slots:
@@ -119,8 +119,7 @@ parts:
     # more information on plugins here: https://snapcraft.io/docs/supported-plugins
     plugin: autotools
     source: https://github.com/sleuthkit/sleuthkit.git
-    source-branch: develop
-    #source-tag: sleuthkit-4.12.0
+    source-tag: sleuthkit-4.12.1
     build-environment: [JAVA_HOME: /usr/lib/jvm/java-17-openjdk-amd64]
     # information on packages here: https://snapcraft.io/docs/package-repositories
     build-packages:
@@ -174,7 +173,7 @@ parts:
       - lsof
     plugin: nil
     source: https://github.com/sleuthkit/autopsy.git
-    source-branch: develop
+    source-tag: autopsy-4.21.0
     build-environment:
       - JAVA_HOME: /usr/lib/jvm/java-17-openjdk-amd64
       - TSK_JAVA_LIB_PATH: $SNAPCRAFT_STAGE/usr/local/share/java
@@ -186,7 +185,7 @@ parts:
       AUTOPSY_PLATFORM_PATH="$AUTOPSY_SRC_PATH/netbeans-plat/$NETBEANS_PLAT_VER"
       AUTOPSY_HARNESS_PATH="$AUTOPSY_PLATFORM_PATH/harness"
       export TSK_HOME="$HOME/parts/sleuthkit/build"
-      ant -Dnbplatform.active.dir="$AUTOPSY_PLATFORM_PATH" -Dnbplatform.default.harness.dir="$AUTOPSY_HARNESS_PATH" build build-zip
+      ant -Dnbplatform.active.dir="$AUTOPSY_PLATFORM_PATH" -Dnbplatform.default.harness.dir="$AUTOPSY_HARNESS_PATH" build-zip
 
       # ----- SETUP EXTRACT DIRECTORY -----
       AUTOPSY_LOCATION="$SNAPCRAFT_PART_INSTALL/autopsy"