Restoring an older version of Firefox is actually not that difficult at all. I ran it from time to time to check for updates, and the latest update today resolved the issue.
The core benefit for me was that I could simply switch to Aurora without touching the Nightly version at all. I decided to use Firefox Aurora in the meantime, but the second option would have worked as well. It did not, which left me with two options: use a different channel of Firefox in the meantime or go back to the Nightly version that worked just fine. I was not too worried about that at the time as I knew that Nightly versions of the browser sometimes had hiccups like this, and that the next update would likely fix the issue again. I got weird black bars on the screen that would move around on mouse movement and made it impossible to work with the browser at all. My Firefox Nightly version that I have been running for some time now received an update two days ago that rendered it completely unusable.
