For those who are getting their Firefox messed up, the binary from the Mozilla site works just fine and is far more respectful.
I'm using Mate 22.04 LTS. A few settings has to be done to disable updates behind your back, but at least these settings persist, unlike when I was using Snap or whatever it was I managed to install via apt (I think it still eventually reverted to Snap). There was also the issue that the Snap version disables some extensions (sure they are potentially dangerous, but that risk is for me to take).
Now, I just manually update Firefox at convenient times via the Help -> About menu.