Maybe they’ve finally fixed those problems. In Lakka, I set my controller up once (for each unique controller) in RetroArch frontend, and then it works in any emulator core. I don’t think it’s normal to have to set up the controller in each core (but you can, if you want or need to!)
This; works on Mull; there is no submit button, it just constantly refreshes the results and thus is slow AF from continuously juggling the data.