In somewhat typical fashion, Google have changed how Back handling works in the newest Android SDK but have not, predictably, made the new way usable from the NDK. Hopefully they will by the time the opt out stops working but I ain’t holding my breath tbh

Random discovery I’ll share in case it helps a future traveller (or future me): the native C++ SDK for Google Play Games hasn’t been updated to support 16KB page size, making it now functionally unusable. You need to JNI bridge across to the Java SDK.

Coming to the disappointing conclusion that developing games for Android without any Java at all is impractical enough as to be impossible.