Sorry to bump an old thread but I managed to get hello_xr running on Quest. It took me a while since I couldn't find any detailed/up-to-date instructions around and I'm pretty new to Android. I wrote up the process in case anyone finds it useful:
We have added documentation to the Oculus developer site for how to use hello_xr: https://developer.oculus.com/documentation/native/android/mobile-build-run-hello-xr-app/
Hopefully these docs will be useful for some folks.