when I switched my audio processing from Windows based Cubase to Ubuntu based Ardour I was facing the same problem my: my M-AUDIO interface just didn’t show up in the system. It was frustrating!
Now there are two ways to approach this. You can either check for solutions or post yourself in one of the forums e.g. here https://ubuntuforums.org/archive/index.php/t-2405905.html
… or you can switch your hardware device to one which is more compatible to Ubuntu. What I did was really straightforward … if you’re on a budget simply sell your interface on Craigslist or whatever is available in your country. At the same time look for hardware that is most likely compatible. I don’t know what hardware you have but my research back done revealed that focusrite interfaces hardly cause problems. If you’re really unsure you could order from a shop with a good return policy.
Might sound like a bummer but it’s a lot faster than going crazy over incompatible hardware.
Please keep us posted, cheers Tom