Does this work with any app or just second party ones? Can you re-enable it?

How does this affect “second-party” apps (i.e. apps you have created yourself)? Are you still allowed to go to Android studio, make an APK, transfer it to your own phone, and install that app? If no, this spells the death of experimental indie developers on Android.

Yeah forgot to mention the lack of ads and the reliable access anywhere part

I still use mp3s because:

1. No financial cost
2. Not tied to any one app or service
3. More customization: Can be played back at any speed or modified in some other way