AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
        package="com.my_domain.app.helloactivity">
        
    <application android:label="@string/app_name">
    
        <activity class=".HelloActivity">
            <intent-filter>
                <action android:value="android.intent.action.MAIN"/>
                <category android:value="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity>
        
    </application>
    
</manifest>

Any package that will be presented to the user as a top-level application available from the program launcher will need to include at least one Activity component that supports the MAIN action and LAUNCHER category as shown here.

CODE