This is kind of a funny coincidence. Back in 2010 I needed a mixer I could easily remotely control and started to build a setup with a laptop and an M-Audio Fast Track Ultra 8R (FTU8R). I soon found out that the FTU8R wasn't exactly working under Linux, though, so I started digging into it, got people with more knowledge into it (Daniel Mack) and when finally Aurelein Leblond donated a FTU for development to Daniel we finally got support for these an similar devices in Linux. (I just did the mixer controls).

I switched to a Berhigner XR18 as son as they were available: It was all I ever wanted in a singel box. Switched to the Midas MR18 last year. It works perfectly for my needs, I get much better latency without XRuns than I ever did with the FTU8R.

This being said, just *today* I resurrected my FTU8R after almost 4 years for the first time for a new project. Mine works fine.

Most of the times when the FTU8R sound really ugly it's either
a) Some FX that have not been muted.
b) interference of the direct output with the signal through the computer.

Check your mixer settings either with alsamixer or FTU-Mixer:
https://github.com/JonasSC/FTU-Mixer .

If FTU-Mixer crashes, like it did for me on Fedora 28, try my fixed (?) version of it:

https://github.com/showlabor/FTU-Mixer

Good luck and, please, give some feedback so we know if it worked.

Kind regards,
Felix