Unfortunately, I don't have a solution, but I have the same issue on different devices (also on macOS 11.6.2, installed the most recent driver).
I have a Babyface Pro FS, and a Digiface USB. Both are not recognized as audio devices in macOS anymore.

I just figured out a strange thing:
When opening the firmware update tool "RME USB Series Flash Tool" while both devices are connected, they both show up in the dropdown menu. First I thought it might be cached or so, so I disconnected one device --> It showed just the connected device in the dropdown list; Disconnected both --> "RME USB Series Flash Tool" closed immediately after start.

So it seems like the USB connection is working. The devices just do not show up as audio devices in macOS.

*Edit: Using Class Compliant mode on iPad also works fine (using Babyface Pro FS, not tested on Digiface USB)

I'm sorry, but it doesn't work.
At least on my computer.
I accurately followed these instructions and still can't open the TotalMix window...

Help !

So, here is what I tried, and didn't work (the name of my default drive is MacDavid) :

- boot into recovery mode
- open Terminal
- run the kernel extension panic medic boot command by typing: kmutil trigger-panic-medic --volume-root/Volumes/MacDavid

Then I had this message : Missing expected argument '--volume-root <volume-root>'

Nothing else happened.

And I hadn't to allow anything when I opened Security&Privacy after rebooting.
The Fireface still doesn't appear as un usable device. Even after re-installing the latest driver.

So, I'm totally blocked.