[dominicperry]

OK, so as a check, if you disconnect the Carbon and use another audio interface (internal or external), do you still get the startup hangs?
If you do, I would look at trying to find out why PT isn't behaving well. If not, then that's a weird problem.

In fact, either way, you have plenty of power, no complications with your connection to Carbon and a supported configuration. I would raise a ticket with Avid.

Personally, I think Monterey works better than Big Sur, but my experience is limited to an M1 machine - (my Mac Pro 7.1 is still on Catalina and works fine with Carbon). But you may not want to upgrade from Big Sur to Monterey, especially as it won't necessarily help.

Your experience is not unique, but it's not clear to me why some people have problems and others do not.

Dominic