Librewolf comes packaged by my distro (GNU Guix) so that’s what I use. I’m sure most “privacy” or “hardened” Firefoxes are more or less interchangeable. The only one that’s really noteworthy is GNU IceCat, because it’s more focused on software-freedom and includes the LibreJS addon, but I switched to Librewolf once it was packaged for Guix.