Opt-out of Android App Bundle after accepting by accident
From Google Play Console
As they stated below , I don't think this is possible .
App Signing by Google Play Terms of Service Effective as of May 8, 2018
- Permanent Enrollment
3.1. It will not be possible to retrieve Your app signing key once it is provided to or generated by Google. Google may retain indefinitely a backup copy of the key(s) for disaster recovery purposes.
3.2. You can unpublish Your app and publish a new app with a new package name, without opting into the Service, at any time.
So In that case . you need to upload your apk with new package name and without opting into App bundle.
Only App Signing by Play is a one-way enrollment. You can still upload APKs if you prefer.
Edit: Just to clarify, enrolling in App Signing by Play and uploading App Bundles are decoupled: you can still upload APKs even when enrolled in App Signing by Play.
On a side-note, should you choose to try App Bundles again, I would recommend you to test your app using APKs generated from the App Bundle. You can do this using bundletool as you found out, but also directly from Android Studio. See this answer. Using the internal testing tracks from the Play Console also allows you to test exactly what will be delivered to your users.