Agent's unfinished attempt to convert the project from AppCompat to AndroidX.

app/src/main/AndroidManifest.xml

@@ -2,8 +2,7 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools">
 
-    <!-- Include required permissions for Google Mobile Ads to run. -->
-    <uses-permission android:name="android.permission.INTERNET" />
+    <uses-sdk android:minSdkVersion="21" />    <uses-permission android:name="android.permission.INTERNET" />
     <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
 
     <application