Rocksmith 2014 Real Tone Cable not detected on Bazzite Linux

Hi all. Hope to find a fix please.
"Running Rocksmith 2014 on Bazzite with Proton Experimental. Linux detects the Real Tone Cable fine (shows as card 3 in arecord -l) but the game says cable is unplugged.

Already tried:

• protontricks 221680 sound=alsa
• Rocksmith.ini ExclusiveMode=0 and Win32UltraLowLatencyMode=0
• Cable does not appear in winecfg Audio tab input dropdown

Any ideas?
Much appreciated