I've switched from librewolf to mullvad browser, it is tor browser minus the tor network.

In other words it makes all its users have the same fingerprint so that they can blend together. This is much more effective at detetring tracking than simply hiding or randomizing details like librewolf does.

In this thread the arkenfox Dev goes as far to say "PS: long term I am hoping we can retire arkenfox (I can't speak for LW) and just use MB - but they're just a little too divergent for now"

https://github.com/mullvad/mullvad-browser/issues/1

Other options (besides tor browser) are librewolf or Arkenfox, no other firefox forks are reputable from a security/privacy perspective