My problem is now resolved. Whew. Details below:Could you describe the process that "fixed" your problem updating? My Mac Studio+Studio Display has for over 30 minutes been sitting on the screen saying it's updating. The text says: "The screen may turn off for a few minutes during this firmware update. Do not disconnect or power off your Apple Studio Display". Of course I'm reluctant to disturb it but it's clearly not going to finish.
What did you do?
After an hour of staring at the screen saying it is updating, don't disconnect, I called AppleCare. The person I spoke with was nice but also didn't know anything. Eventually he said shut down the Mac which I did and then restarted it. Everything came up as normal. We checked the firmware version on the display in a system profile and it had the updated software version. So the update apparently worked as expected EXCEPT at the end it didn't show a finished result and shared the sh*t out of me. But it's working as expected now.