How to install GNOME Shell Extensions using Firefox Snap? [duplicate]
Solution 1:
Update 20220203 - the bug 1947501 is fixed since 20211103.
So all you need is to run the below commands:
sudo snap remove firefox
sudo apt-get install --reinstall firefox
If you need historic information - check previous revisions of this answer. But keep in mind that running sudo apt-mark manual firefox may be still needed if you install Ubuntu 21.10 flavor using offline installation.