Firefox is at the moment the best option worth supporting
>what about Librewolf or Mullvad's browser or Icecat, or etc..
any of those forks basically depend on Firefox and Mozilla to do the heavy development lifting so to speak. They're customization. That's fine, but you need to be invested in the success of Firefox for any of those others to have a real future. Firefox is the primary bastion against Google basically owning the web - and fucking off and going to histrionics to some fork AND THEN BITCHING ABOUT FIREFOX ITSELF for inane shit like easy to disable FOSS, transparent, telemetry, isn't going to help in the long run. This doesn't mean Mozilla or Firefox shouldn't be critiqued but shit realize what we're up against here. Ever since the Chrome/ium surge they're not just one major browser but basically have de facto control of the web standards and usage. The more Firefox users (no matter if they're using a fork or some kind or arkenfox or some custom shit of their own) the better to ensure that web dev isn't done only with interest in having Chrome/ium or Blink rendering tested.