sorry for the insanely late reply.
This doesn’t look fixable. If the Android OS reports a button as the back button, we would have to dive into figuring out what controller it is and modifying the behavior based on that. Besides the fact that we couldn’t possibly get this right for all controllers, we would now be inconsistent across different android controllers, with players expecting the back button to open the leave game menu, but on some devices it does something different.
This mostly seems like a weird choice on Nvidia’s part, I don’t know why they omitted a select button when the Android gamepad API has one (KeyEvent | Android Developers).