I also struggled with getting my 8bitdo Ultimate controller to work on Linux. My solution ended being to use a Mayflash controller adapter to trick my PC into thinking it was just a normal Xinput controller, while the adapter itself thought it was a Switch Pro Controller. I’ve since become a huge fan of these little adapters, as they basically make any controller compatible with any platform, including Linux, so that’s one less annoying compatibility issue to deal with.
I also struggled with getting my 8bitdo Ultimate controller to work on Linux. My solution ended being to use a Mayflash controller adapter to trick my PC into thinking it was just a normal Xinput controller, while the adapter itself thought it was a Switch Pro Controller. I’ve since become a huge fan of these little adapters, as they basically make any controller compatible with any platform, including Linux, so that’s one less annoying compatibility issue to deal with.