Thanks to the folks from Briar actually doing all the work I got their code fully refactored and actually ran a real end to end test with a Tor hidden service where the Tor Onion Proxy was created, initialized and run programmatically on Android.
This means we now have all the code to get a TDH to act both as a Tor client and a Tor Onion Proxy programmatically on Android!
Note that the binary being used ONLY runs on ARM so the Android x86 emulator will not work. For now I'm using my test phone.
Right now this code lives in my fork (https://github.com/yaronyg/Tor_Onion_Proxy_Library). I'll PR it to the main repro when I have the Java code also working. I also need to add in a few more smoke tests but nothing major.