So, there is no way to make this work? :(
I don't think so, but since it's also not working in Windows, the board may be broken ?
I found this mail chain reporting some fix in Ubuntu 19.10 for another very similar Saulabi model, I don't know if helps in any way : https://www.mail-archive.com/search?l=ubuntu-bugs@lists.ubuntu.com&q=subject:"[Bug+786955]+Re%3A+Saulabi+4K+Joystick+(Buttons+not+working)"&o=newest&f=1
That doesn't seem to have any useful information for your problem.