Just spent the afternoon debugging in Logcat / Android Studio
It would appear that using AppLovin under Gideros 2019.10 and using Google Play Services >16.0.0, that the built .apk will crash on real target device on boot. It seems Google Play changed something about the package name in Google Play Services 17.0.0 onwards that causes problems with the AppLovin libs when compiled by Gideros 2019.10.
Unity is fine but it is why my own ads rotator broke until I realised the above today.
I have it all working now but thought I would mention this here.
I only use AppLovin and Unity these days on Android/iOS with the exception of Amazon apps where I still have some live Charboost intergrated apps. Don't want to touch those as they make money as is. Charboost no longer functions correctly with newer Gideros releases over the last year (it compiles OK but you won't see any ads). I told them about that ages ago but they have no interest in supporting Gideros SDK built apps it seems.