diff --git a/.github/workflows/dotnet-build.yml b/.github/workflows/dotnet-build.yml
index 3e9e95bd..c87d1613 100644
--- a/.github/workflows/dotnet-build.yml
+++ b/.github/workflows/dotnet-build.yml
@@ -31,6 +31,7 @@ jobs:
         uses: actions/checkout@v4
         with:
           fetch-depth: 0
+          submodules: true
 
       # Set up a VS build environment.
       - name: Setup Environment Variables
@@ -64,9 +65,9 @@ jobs:
         run: .\build\Install-WindowsSdkISO.ps1 18362
         shell: pwsh
 
-      # Run the build.
+      # Run the build. Pushes to main and rel/* also build the full multi-arch sample app bundles.
       - name: Build
-        run: .\build.ps1 --target=Package
+        run: .\build.ps1 --target=Package ${{ github.event_name == 'push' && (github.ref == 'refs/heads/main' || startsWith(github.ref, 'refs/heads/rel/')) && '--fullAppBuild=true' || '' }}
         shell: pwsh
         working-directory: .\build
 
diff --git a/build/build.cake b/build/build.cake
index d881231a..1c27469a 100644
--- a/build/build.cake
+++ b/build/build.cake
@@ -11,6 +11,8 @@ using System.Text.RegularExpressions;
 
 var target = Argument("target", "Default");
 var configuration = Argument("configuration", "Release");
+// Builds the sample app bundles for every architecture. Slow; not needed for the NuGet packages.
+var fullAppBuild = Argument("fullAppBuild", false);
 
 //////////////////////////////////////////////////////////////////////
 // VERSIONS OF TOOLS TO USE
@@ -61,6 +63,10 @@ void MSBuildSolution(
         {
             settings = settings.WithProperty(property.Name, property.Value);
         }
+        if (!fullAppBuild)
+        {
+            settings = settings.WithProperty("AppxBundle", "Never");
+        }
         return settings;
     }
 
@@ -94,6 +100,7 @@ static bool IsExcludedDirectory(FilePath path)
 
     return
         segments.Contains("bin") ||
+        segments.Contains("external") ||
         segments.Contains("internal") ||
         segments.Contains("obj");
 }