Google Play will start requiring new apps to be published as Android App Bundles (AAB) starting in August 2021. This will replace the APK as the standard publishing format.
Using Appflow? You're already covered. The Native Builds feature automatically creates an APK and an AAB binary for you, and with Deploy to App Stores, an AAB binary can be automatically sent to Google Play as well.
If you haven’t made the switch to app bundles yet, you would likely need to opt-in Play App Signing to be able to publish AABs. To help with the Play App Signing adoption, we’ve put together a guide that walks you through enabling Play App Signing in this article.