Pentadactyl nightlies are always compatible with the latest FF version. The one on the official addon website probably hasn't been updated in over a year.

Pentadactyl and Tab groups are the reason I can't drop FF. Chromium has its own alternatives to these, but vimium has nothing on penta and all tab group addons I've tried are nowhere near stable.

I'll drink to that. This problem was a major part of my post-graduate studies, but not so much in my current research. Such things have a way of affecting an entire spectrum of scientific disciplines, though.