AFAIK the only two really worth bothering with that are still updated today are Pale Moon and Waterfox. Either one are fine to use, I suppose, but have their own issues. ie. Pale Moon is based on a much older version of Gecko (the browser engine that Firefox uses, in this case it's based on Firefox 38, released in like 2015) so you might not see any of the improvements modern Firefox has incorporated in newer releases than that.
On the other hand, Waterfox uses modern Gecko version (particularly based on version 78 of Firefox)...but was bought by an advertising company just last year, which could be an issue for anyone who cares about privacy in the future.
I used Waterfox back in the day when there was no official 64-bit build of Firefox, but that hasn't been the case for many years. I'm genuinely unsure why people use anything other than official Firefox browsers (when using Firefox browsers) these days.
@WiiMiiSwitch I'm not sure one blog post by one blogger is sufficient to say Mozilla has gone political, particularly when the blog post didn't even seem to take a stance on whether or not deplatforming the former president was the right thing to do. It looks to me Mozilla is trying to get into the web traffic business, not "go political."