By the way, it might be that the controller issue is solved by using a newer SDL version than the once bundled with FS-UAE 3.0.5 (Don't know that for sure). Other updated libraries (Qt and Python) might fix other issues.
Please try the x86-64 version I posted in
http://eab.abime.net/showthread.php?t=106794 and see if that improves anything for Big Sur (with or without M1 hardware).