I cannot really be happy about being on Librewolf, because I am very afraid Firefox might eventually ditch MV2 as well. Mozilla is dependent on Google and is known for questionable choices, so...
Firefox supports MV3, with some tweaks such as the WebRequest limitations added by Google's MV3 being removed from the Firefox implementation. I don't think they will remove it
This would be the same problem as in Chromium - you theoretically can, but in practice maintaining it with zero support from the original company would get increasingly hard.