diff --git a/covid19_mobile_app/android/app/src/debug/AndroidManifest.xml b/covid19_mobile_app/android/app/src/debug/AndroidManifest.xml
index 70df909..f880684 100644
--- a/covid19_mobile_app/android/app/src/debug/AndroidManifest.xml
+++ b/covid19_mobile_app/android/app/src/debug/AndroidManifest.xml
@@ -1,5 +1,4 @@
-<manifest xmlns:android="http://schemas.android.com/apk/res/android"
-    package="com.example.covid19_mobile_app">
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
     <!-- Flutter needs it to communicate with the running application
          to allow setting breakpoints, to provide hot reload, etc.
     -->
diff --git a/covid19_mobile_app/android/app/src/profile/AndroidManifest.xml b/covid19_mobile_app/android/app/src/profile/AndroidManifest.xml
index 70df909..f880684 100644
--- a/covid19_mobile_app/android/app/src/profile/AndroidManifest.xml
+++ b/covid19_mobile_app/android/app/src/profile/AndroidManifest.xml
@@ -1,5 +1,4 @@
-<manifest xmlns:android="http://schemas.android.com/apk/res/android"
-    package="com.example.covid19_mobile_app">
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
     <!-- Flutter needs it to communicate with the running application
          to allow setting breakpoints, to provide hot reload, etc.
     -->
diff --git a/documentation/MAINTENANCE.md b/documentation/MAINTENANCE.md
index f056cb1..825f7ab 100644
--- a/documentation/MAINTENANCE.md
+++ b/documentation/MAINTENANCE.md
@@ -30,6 +30,18 @@ make gradle-update FORCE=1                     # latest version, force update
 make gradle-update VERSION=9.7.0 FORCE=1       # specific version, force update
 ```
 
+## Firebase apps
+
+These apps connect to Firebase and need a developer-provided `google-services.json`
+in `<app>/android/app/` before they can be built:
+
+- `firebase_google_authentication`
+- `google_signin`
+- `using_firebase_db`
+
+The file is never committed because it contains your Firebase project config.
+Create a Firebase project for each app and download the file from the Firebase console.
+
 ## Requirements
 
 - `make` (preinstalled on macOS and most Linux systems)
diff --git a/dropdown_button/android/app/src/main/AndroidManifest.xml b/dropdown_button/android/app/src/main/AndroidManifest.xml
index bccbf8c..7661cd5 100644
--- a/dropdown_button/android/app/src/main/AndroidManifest.xml
+++ b/dropdown_button/android/app/src/main/AndroidManifest.xml
@@ -7,11 +7,6 @@
     -->
     <uses-permission android:name="android.permission.INTERNET"/>
 
-    <!-- io.flutter.app.FlutterApplication is an android.app.Application that
-         calls FlutterMain.startInitialization(this); in its onCreate method.
-         In most cases you can leave this as-is, but you if you want to provide
-         additional functionality it is fine to subclass or reimplement
-         FlutterApplication and put your custom class here. -->
     <application
         android:name="${applicationName}"
         android:label="dropdown_button"
@@ -34,5 +29,11 @@
                 <category android:name="android.intent.category.LAUNCHER"/>
             </intent-filter>
         </activity>
+    
+        <!-- Don't delete the meta-data below.
+             This is used by the Flutter tool to generate GeneratedPluginRegistrant.java -->
+        <meta-data
+            android:name="flutterEmbedding"
+            android:value="2" />
     </application>
 </manifest>
diff --git a/enabling_splash_screen/android/app/src/main/AndroidManifest.xml b/enabling_splash_screen/android/app/src/main/AndroidManifest.xml
index 8016c04..2ef7746 100644
--- a/enabling_splash_screen/android/app/src/main/AndroidManifest.xml
+++ b/enabling_splash_screen/android/app/src/main/AndroidManifest.xml
@@ -7,11 +7,6 @@
     -->
     <uses-permission android:name="android.permission.INTERNET"/>
 
-    <!-- io.flutter.app.FlutterApplication is an android.app.Application that
-         calls FlutterMain.startInitialization(this); in its onCreate method.
-         In most cases you can leave this as-is, but you if you want to provide
-         additional functionality it is fine to subclass or reimplement
-         FlutterApplication and put your custom class here. -->
     <application
         android:name="${applicationName}"
         android:label="enabling_splash_screen"
@@ -34,5 +29,11 @@
                 <category android:name="android.intent.category.LAUNCHER"/>
             </intent-filter>
         </activity>
+    
+        <!-- Don't delete the meta-data below.
+             This is used by the Flutter tool to generate GeneratedPluginRegistrant.java -->
+        <meta-data
+            android:name="flutterEmbedding"
+            android:value="2" />
     </application>
 </manifest>
diff --git a/expense_planner/android/app/src/main/AndroidManifest.xml b/expense_planner/android/app/src/main/AndroidManifest.xml
index 6683bd8..a99df03 100644
--- a/expense_planner/android/app/src/main/AndroidManifest.xml
+++ b/expense_planner/android/app/src/main/AndroidManifest.xml
@@ -1,11 +1,6 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
 >
 
-    <!-- io.flutter.app.FlutterApplication is an android.app.Application that
-         calls FlutterMain.startInitialization(this); in its onCreate method.
-         In most cases you can leave this as-is, but you if you want to provide
-         additional functionality it is fine to subclass or reimplement
-         FlutterApplication and put your custom class here. -->
     <application
         android:name="${applicationName}"
         android:label="expense_planner"
@@ -28,5 +23,11 @@
                 <category android:name="android.intent.category.LAUNCHER"/>
             </intent-filter>
         </activity>
+    
+        <!-- Don't delete the meta-data below.
+             This is used by the Flutter tool to generate GeneratedPluginRegistrant.java -->
+        <meta-data
+            android:name="flutterEmbedding"
+            android:value="2" />
     </application>
 </manifest>
diff --git a/google_signin/android/app/src/main/AndroidManifest.xml b/google_signin/android/app/src/main/AndroidManifest.xml
index a9151d5..f5632dc 100644
--- a/google_signin/android/app/src/main/AndroidManifest.xml
+++ b/google_signin/android/app/src/main/AndroidManifest.xml
@@ -7,11 +7,6 @@
     -->
     <uses-permission android:name="android.permission.INTERNET"/>
 
-    <!-- io.flutter.app.FlutterApplication is an android.app.Application that
-         calls FlutterMain.startInitialization(this); in its onCreate method.
-         In most cases you can leave this as-is, but you if you want to provide
-         additional functionality it is fine to subclass or reimplement
-         FlutterApplication and put your custom class here. -->
     <application
         android:name="${applicationName}"
         android:label="google_signin"
@@ -34,5 +29,11 @@
                 <category android:name="android.intent.category.LAUNCHER"/>
             </intent-filter>
         </activity>
+    
+        <!-- Don't delete the meta-data below.
+             This is used by the Flutter tool to generate GeneratedPluginRegistrant.java -->
+        <meta-data
+            android:name="flutterEmbedding"
+            android:value="2" />
     </application>
 </manifest>
diff --git a/handling_routes/android/app/src/main/AndroidManifest.xml b/handling_routes/android/app/src/main/AndroidManifest.xml
index 3bbcb5d..168e76a 100644
--- a/handling_routes/android/app/src/main/AndroidManifest.xml
+++ b/handling_routes/android/app/src/main/AndroidManifest.xml
@@ -7,11 +7,6 @@
     -->
     <uses-permission android:name="android.permission.INTERNET"/>
 
-    <!-- io.flutter.app.FlutterApplication is an android.app.Application that
-         calls FlutterMain.startInitialization(this); in its onCreate method.
-         In most cases you can leave this as-is, but you if you want to provide
-         additional functionality it is fine to subclass or reimplement
-         FlutterApplication and put your custom class here. -->
     <application android:name="${applicationName}" android:label="handling_routes" android:icon="@mipmap/ic_launcher">
         <activity android:name="io.flutter.embedding.android.FlutterActivity"
                   android:exported="true"
@@ -25,5 +20,11 @@
                 <category android:name="android.intent.category.LAUNCHER"/>
             </intent-filter>
         </activity>
+    
+        <!-- Don't delete the meta-data below.
+             This is used by the Flutter tool to generate GeneratedPluginRegistrant.java -->
+        <meta-data
+            android:name="flutterEmbedding"
+            android:value="2" />
     </application>
 </manifest>
diff --git a/image_editor/android/build.gradle.kts b/image_editor/android/build.gradle.kts
index dbee657..93fdcd6 100644
--- a/image_editor/android/build.gradle.kts
+++ b/image_editor/android/build.gradle.kts
@@ -16,6 +16,17 @@ subprojects {
     project.layout.buildDirectory.value(newSubprojectBuildDir)
 }
 subprojects {
+    // gallery_saver_plus hardcodes compileSdk 31, which its dependencies no
+    // longer support. Register the override before forcing :app evaluation so
+    // it runs after each library script has set its own value.
+    project.afterEvaluate {
+        if (project.plugins.hasPlugin("com.android.library")) {
+            val appSdk = (project(":app").extensions.getByName("android")
+                as com.android.build.api.dsl.ApplicationExtension).compileSdk
+            (project.extensions.getByName("android")
+                as com.android.build.api.dsl.LibraryExtension).compileSdk = appSdk
+        }
+    }
     project.evaluationDependsOn(":app")
 }
 
diff --git a/image_from_network/android/app/src/main/AndroidManifest.xml b/image_from_network/android/app/src/main/AndroidManifest.xml
index 78ed7e9..d59f48c 100644
--- a/image_from_network/android/app/src/main/AndroidManifest.xml
+++ b/image_from_network/android/app/src/main/AndroidManifest.xml
@@ -7,11 +7,6 @@
     -->
     <uses-permission android:name="android.permission.INTERNET"/>
 
-    <!-- io.flutter.app.FlutterApplication is an android.app.Application that
-         calls FlutterMain.startInitialization(this); in its onCreate method.
-         In most cases you can leave this as-is, but you if you want to provide
-         additional functionality it is fine to subclass or reimplement
-         FlutterApplication and put your custom class here. -->
     <application
         android:name="${applicationName}"
         android:label="image_from_network"
@@ -34,5 +29,11 @@
                 <category android:name="android.intent.category.LAUNCHER"/>
             </intent-filter>
         </activity>
+    
+        <!-- Don't delete the meta-data below.
+             This is used by the Flutter tool to generate GeneratedPluginRegistrant.java -->
+        <meta-data
+            android:name="flutterEmbedding"
+            android:value="2" />
     </application>
 </manifest>
diff --git a/infinite_list/android/app/src/main/AndroidManifest.xml b/infinite_list/android/app/src/main/AndroidManifest.xml
index 4b7e588..8769e35 100644
--- a/infinite_list/android/app/src/main/AndroidManifest.xml
+++ b/infinite_list/android/app/src/main/AndroidManifest.xml
@@ -7,11 +7,6 @@
     -->
     <uses-permission android:name="android.permission.INTERNET"/>
 
-    <!-- io.flutter.app.FlutterApplication is an android.app.Application that
-         calls FlutterMain.startInitialization(this); in its onCreate method.
-         In most cases you can leave this as-is, but you if you want to provide
-         additional functionality it is fine to subclass or reimplement
-         FlutterApplication and put your custom class here. -->
     <application
         android:name="${applicationName}"
         android:label="infinite_list"
@@ -34,5 +29,11 @@
                 <category android:name="android.intent.category.LAUNCHER"/>
             </intent-filter>
         </activity>
+    
+        <!-- Don't delete the meta-data below.
+             This is used by the Flutter tool to generate GeneratedPluginRegistrant.java -->
+        <meta-data
+            android:name="flutterEmbedding"
+            android:value="2" />
     </application>
 </manifest>
diff --git a/using_firebase_db/android/app/src/main/AndroidManifest.xml b/using_firebase_db/android/app/src/main/AndroidManifest.xml
index 73de986..f148971 100644
--- a/using_firebase_db/android/app/src/main/AndroidManifest.xml
+++ b/using_firebase_db/android/app/src/main/AndroidManifest.xml
@@ -1,11 +1,6 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
 >
 
-    <!-- io.flutter.app.FlutterApplication is an android.app.Application that
-         calls FlutterMain.startInitialization(this); in its onCreate method.
-         In most cases you can leave this as-is, but you if you want to provide
-         additional functionality it is fine to subclass or reimplement
-         FlutterApplication and put your custom class here. -->
     <application
         android:name="${applicationName}"
         android:label="using_firebase_db"
@@ -28,5 +23,11 @@
                 <category android:name="android.intent.category.LAUNCHER"/>
             </intent-filter>
         </activity>
+    
+        <!-- Don't delete the meta-data below.
+             This is used by the Flutter tool to generate GeneratedPluginRegistrant.java -->
+        <meta-data
+            android:name="flutterEmbedding"
+            android:value="2" />
     </application>
 </manifest>