I have the M-Audio Fast Track Ultra 8R audio interface which works great on Linux: all the internal routing is exposed in alsamixer including changing the effects on the internal DSP, the only thing I haven’t tried is MIDI and S/PDIF since I can’t find the breakout cable for it anymore. I know this is not strictly on-topic on Ardour forums but this is the only place I could think of where free software, DAW’s, Linux and macOS are all relevant to a certain extent, so I hope you’ll forgive me.