Also experiencing same issue: notifications are not displayed after upgrading to Monterey (12.0.1) on 2020 M1 MacBook Pro. They exist in Notification Center, but are not displayed on screen.
Disconnecting the DisplayLink hub (
Plugable) or quitting DisplayLink Manager (1.5.0, build 58.125) brings notifications back to normal.
Also worth mentioning, my DisplayLink monitor is my second external display and not my main display. Notifications should get shown on my main display (the non-DisplayLink display).
UPDATE: After ticking the "When mirroring or sharing the display" checkbox in Notifications, notifications have reappeared. This was not previously necessary. I present quite often and connect to a projector, so I'd rather not have notifications on while mirroring my display. Is there a fix in sight? Or is this just how things work now. Again, it was not necessary to enable this in Big Sur.
Happy to provide more info as needed.