Previously, I already had it working connected to the same computer with a recent firmware and driver, so I had already gone to security and privacy settings to ‘allow’  RME device to be activated. Then I my iMac’s fusion  hard-drive died on me. I replaced it with an SSD, got it back from repair with Ventura  installed (13.6.7). 

In USB mode it no longer works with the computer.  The Totalmix window doesn’t open. Reinstalling the driver doesn’t help.  I even reinstalled MAC OS.  Nothing helps.
The iMac’s system report lists the interface among the connected USB devices.
In CC mode, it connects to my iPad and works perfectly.

Most confusingly, the Flash tool SOMETIMES gets the correct info from the UCX II:
USB: 106
DSP: 34
Class-compliant 104
Fallback usb: 42
But sometimes, it’s correct only for USB (106),  and everything else has 0.

I’ve reached out to support, but in 7 email exchanges we’ve managed to only clarify my own ineffective attempts to solve the problem.

Thanks for your help!
This is my second RME interface, which I use with the quadmic ii after 10 years on a FF800.