After the newer (post 47?!) FF update, cynwoody integrated his add-on to be able to install directly to FF, without greasemonkey/tampermonkey ( had both installed). I remember having issues after the update, and he explained it to me, at the time.
Brave, if I remember correctly, has steps to install Chrome add-ons, which I followed, but it still isn’t showing up :/
I may look into it again later.
(Oh, P.S. I don’t think it would be a FRTree viewer issue, unless it has something to do with permissions..)
Yay! :D
Played around with it a bit more.. FINALLY got it working on Brave.
Now, I need to see if they have uBlock and uMatrix for Brave.