I hope you find a solution, but also important, I hope you find a better browser. I switched to Brave, maybe there’s an argument to be made that it’s the same as firefox/chrome… but that’s not the experience I’ve had.

Firefox updates just like any browser, then after you also need to update meta mask. You should probably find where the extension stores data and try to make a copy before you do the updates. Also, once you have it working again it’s easy to export your account/seed info and you should back it up so you don’t lose it again.