The issue of multiple API-ABI. Do you have several phones emulated with Android Studio and test your games on each of them? Will a game compiled for API 28 always work on ABI 30, but not vice versa? And the same with NDK. It is something that is causing me a problem, working with the correct versions. I have had to go back to UE4.27.
Another thing, does this diversity of platforms really exist within mobile phones? Or are there one or more that are the most common and in practice everyone compiles for that platform?