What are the best ways to use a phone/tablet as a controller for a local game hosted on a pc/console?

Games like Sunderfolk, or even the jackbox games? I guess the difference is Jackbox uses a browser implementation to send stuff between server and client and something like Sunderfolk has a dedicated app (I assume, have not played it yet). I'd like to make something similar (as a proof of concept at the very least) but I'm finding it hard to find any good resources on how to build something like that. Are there any tutorials I might have missed?