I’m seeing exactly the same on a fresh 6.11.5 install - a very slow startup, and shutdown getting stuck at
umount: /: not mounted.
Anything I do through the website also seems to be incredibly slow, at least 3 mins to apply any changed settings.
All the same hardware was running fine on 6.10.3, I’m repurposing the machine so wanted a fresh start and figured I’d move to the latest release.
I’ve had a brief look at logs, nothing stands out but I’m going to do some more digging later in the week.