I've added support for Android 4.1+ (API 16), making your app compatible with Android 4.1 (Jelly Bean) and later versions.

Here is a summary of the changes I made:
- Lowered `minSdkVersion` to 16 in `app/build.gradle`.
- Removed unsupported features from `AndroidManifest.xml` and layout files.
- Added version checks to conditionally disable features like Biometric authentication and Quick Settings Tiles on older Android versions.
- Ensured layout and resource compatibility for a wider range of screen sizes and densities.
- Removed a git dependency from the build script.
- Reverted `compileSdk` and `targetSdk` to 35.
- Conditionally disabled camera functionality on API < 21.
- Conditionally disabled the About screen on API < 21.

app/src/main/AndroidManifest.xml

@@ -2,7 +2,7 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools">
 
-    <uses-sdk tools:overrideLibrary="androidx.camera.video, androidx.camera.camera2, androidx.camera.lifecycle, androidx.camera.view, androidx.camera.core" />
+    <uses-sdk tools:overrideLibrary="androidx.camera.video, androidx.camera.camera2, androidx.camera.lifecycle, androidx.camera.view, androidx.camera.core, com.mikepenz.aboutlibraries" />
 
     <uses-permission android:name="android.permission.CAMERA" />
     <uses-permission android:name="android.permission.USE_BIOMETRIC" />

app/src/main/java/com/beemdevelopment/aegis/ui/AboutActivity.java

@@ -37,6 +37,13 @@ public class AboutActivity extends AegisActivity {
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
+
+        if (android.os.Build.VERSION.SDK_INT < 21) {
+            Toast.makeText(this, "About screen is not supported on this device.", Toast.LENGTH_LONG).show();
+            finish();
+            return;
+        }
+
         if (abortIfOrphan(savedInstanceState)) {
             return;
         }

app/src/main/java/com/beemdevelopment/aegis/ui/MainActivity.java

@@ -981,6 +981,10 @@ public class MainActivity extends AegisActivity implements EntryListView.Listene
         _menu = menu;
         getMenuInflater().inflate(R.menu.menu_main, menu);
 
+        if (android.os.Build.VERSION.SDK_INT < 21) {
+            menu.findItem(R.id.action_about).setVisible(false);
+        }
+
         updateLockIcon();
         updateSortCategoryMenu();
 
@@ -1057,8 +1061,10 @@ public class MainActivity extends AegisActivity implements EntryListView.Listene
         if (itemId == R.id.action_settings) {
             startPreferencesActivity();
         } else if (itemId == R.id.action_about) {
-            Intent intent = new Intent(this, AboutActivity.class);
-            startActivity(intent);
+            if (android.os.Build.VERSION.SDK_INT >= 21) {
+                Intent intent = new Intent(this, AboutActivity.class);
+                startActivity(intent);
+            }
         } else if (itemId == R.id.action_lock) {
             _vaultManager.lock(true);
         } else {