Did you allow your DAWs access to the microphone in System preferences/Security & privacy?

There are problems with Big Sur. And some of these problems are present for everyone. These get fixed rapidly. Other problems only affect a minority of users and these often don't get fixed soon.

It's not a general RME problem, I think.

I suspect it's because Apple wants to get rid of kernel extensions. These are replaced by system extensions. The difference is, system extensions shouldn't be able to take the entire kernel down.

Apple has also introduced malware prevention and blocking tools since 10.6.4. And sometimes, that blocking tool decides to block system extensions for no good reason.  The latest incarnation also includes notarisation. That's a way to prevent any unknown software from installing/running.

You could go to

System preferences/Security & privacy

and set it to allow software from any source and see if that helps. Sometimes, notarisation seems to forget about already approved software, especially after an update.