Ha, you're here! I ran your updated versions in WaterFox for awhile. Was very happy and it worked perfectly. Thanks! I believe I read something back then about WaterFox eventually also phasing out XPCOM extensions.
Did not know about the shim. Will give it a try. You just gave me some new hope. Thanks again!
[1]: https://github.com/akhodakivskiy/vimfx/releases [2]: https://github.com/girst/legacyfox