I've had good luck with Palemoon, too. Fast and reliable, just like FF once was.
It does have a few minor quirks, though. And its add-on library is limited. (The whole add-on concept is so unstable now between browser releases that it's become a huge mess for users, especially of FF).
Note that you can define multiple profiles with Palemoon just as you can with FF, but you do it using this line command to enter the profile manager --
%> palemoon -p
One thing some people do is to install a whole bunch of browsers. That way there's always something that does what you want if you happen to hit quirks (such as browser extensions that only work with certain versions, bugs, different html rendering, etc).
Among some to consider installing -- FF, Palemoon, Qupzilla, Epiphany, Seamonkey, Opera, Brave, Midori, TOR browser, Chromium. Some are in the standard repository (FF, Qupzilla, Epiphany, Midori) and some are not (Palemoon, Seamonkey, Brave, etc).