I remember that it required me to restart whenever I opened a new tab, or I wouldn't be able to use that tab. Anything in already opened tabs still worked. Then

I remember that it required me to restart whenever I opened a new tab, or I wouldn't be able to use that tab. Anything in already opened tabs still worked. Then I switched from Ubuntu to Debian and I also installed the tar.gz from Mozilla. As you wrote, it updates itself. As a welcome coincidence I checked the version right now and the Help, About Firefox dialog showed me an updating status. There is a updates/0/update.status file in Firefox directory that had the "downloading" content. It's "applied" now. The update.version file contains "122.0" and there is a 20 MB file names "update.mar". The file "last-update.log" contains many "PREPARE PATCH", "EXECUTE PATCH", "FINISHED PATCH" lines on shared libraries file and other files. Apparently the new version is waiting in the updated/ directory. The About dialog still reports 121.0.1 and has a "Restart to update Firefox" button. I'll wait to see what happens and how long I can keep using the current version before having to switch to the new one.