To anyone coming from search engines, I hope this helps out:
I have a UR28M interface and I’m running Debian 9. The USB interface is recognized and sound was coming out but there was reverb on top of everything and I couldn’t seem to change the volume of any of the channels without it resetting.
I managed to fix this by turning on Class Compliant mode, described in the manual here: http://download.steinberg.net/downloads_hardware/UR28M/UR28M_documentation/UR28M_OperationManual_en.pdf#G6.1032537
Turn on the device while holding down OUTPUT button C, and keep pressing the OUTPUT C button until an INPUT meter/OUTPUT meter flashes.The UR28M enters Class Compliant mode for Apple iPad connectivity. While in the Class Compliant mode, the power button flashes several times by pressing the power button. To turn off the Class Compliant mode, turn on the power while holding down OUTPUT button C again.
After doing that the reverb was gone and I could listen to audio normally.
Good luck!