The Emulation General Wiki has a few pages on RetroArch:
The Using RetroArch page aims to document how to use it, and solutions to problems. So it is particularly useful. Feel free to add to them.
OK, I guess I’ll link to the Emulation General thread too since it’s pertinent to RetroArch dev a lot of times -
Oh and don’t worry - I will stop shitpushing there and only keeping it to anon technical replies that are (mostly) helpful.