Hello there! Welcome to the forums.
Seems like you’re not alone with trying to get mupen64plus to work.
It needs a whole bunch of dependencies that don’t come included.
It doesn’t use Retroarch. From what I’ve gathered, they aren’t maintaining the Retroarch core anymore for arm7hf. I’ve looked into downloading an older version and running, but haven’t had much luck. I’ll keep trying regardless!
I’ve made a post here with a script that should make everything work.
If you have trouble with that, I’ve got a custom image that I’m maintaining with mupen64plus pre installed, along with a bunch of other things.
Of course, this will unfortunately mean wiping everything. So definitely try doing it all manually first.
Re: pokemon stadium in particular, I’m guessing you’re using the western release, which is actually the Japanese Pokemon stadium 2.
Pokémon stadium (2) has some texture problems where menu items, and trainee faces appear as garbled text; kind of like MissingNo. This is something I remember happening years ago when trying to emulate it on a PC. I think I was using Project 64 back then. Anyway, menus and trainers aside, the game will run. I haven’t thoroughly tested how all the mini games work etc, so do post your findings.