@Patrick30 - I’m definitely not in the best position to comment on adding to odk core as I’m just an independent developer, but the answer from @elmps2018 sounds like a really good starting point.
I definitely think it would be nice to have a few more question types and examples, although I think this current case might not be the best one given the potential incompatibilities we’ve discussed in the thread (one of the things I really like about odk-x is that when things work they seem to work consistently well everywhere).
Another option is would be for some form of template to make it easier for community members like you and me to develop/maintain/showcase/share custom examples that would be of use to others. I know there is a forum thread for showcase, but personally I’d rather some sort of system where you can see the code working in real-time. If we ever get this working it could be a good example case
As for getting things working, the folder you sent works fine for me on Android 7.0 so I think still it’s most likely a device issue. I’d say the easiest way to fix would be to visit https://www.deviceinfo.me/ on your device and send me a copy of the device information displayed via private message (I don’t think this should be of interest to others at this stage, also feel free to remove IP and/or any information that could be sensitive, all I really care about is Device, OS and browser so you could just copy the first few lines) and we can just take it from there.