There's a workaround to support pretty much any FF extension at this point -- but you have to create a "collection" with your firefox account and then point your Android FF install at that collection. Not too hard, but a little bit of a PITA. If you're like me and maintain the same couple dozen extensions on every FF install, though, it actually works pretty well.
FWIW, Mozilla has worked with devs of some popular extensions to get them working on "new" mobile FF, including uBo.