Your old profile wasn't removed along with the deb package, it should still be in ~/.mozilla/firefox/. If you close the firefox snap, delete ~/snap/firefox/common/.mozilla/firefox then re-run the snap, it should attempt to import the existing profiles from the deb again.
Please let us know whether this works. ** Changed in: firefox (Ubuntu) Status: New => Incomplete -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1947257 Title: Partial profile loss on upgrade from 21.04 to 21.10 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/firefox/+bug/1947257/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs