M1 Mac mini here with Big Sur 11.4 and Office 16.49 (Word, Powerpoint and Excel).
Whatever I tried the damned MAU keeps on popping up in the Dock with a badge specifying I'd have 3 updates pending.
I tried following a lot of suggestions from the web to n avail, they seem either outdated or not...
From time to time, I keep getting this notification, even if I delete it.
I tried deleting it from Notifications in System Preferences.
The Microsoft Office is installed from the App Store, I previously had it installed from Microsoft website. I think I uninstalled it using AppCleaner...