I use Mullvad Browser. It’s maintained in coordination with the Tor Project, and is essentially the Tor Browser with Tor itself stripped out. Same browser fingerprinting protections, however, among other things.
EDIT: I’d like to clarify that this has nothing to do with my trust in Mozilla or Firefox itself, especially not concerning recent panics about benign changes. I still use Firefox on the side, it just does not have fingerprinting protections by default, and hardening it manually leads to minor differences between user configurations (even with Arkenfox if that’s still around) that is solved by Mullvad Browser for me. I use Mullvad Browser for my main browsing, and Firefox for specific exceptions. Firefox itself is fine, and no, Mozilla is not burning it to the ground.
Well, the hardening, just as with Tor Browser, does break some sites. It comes preinstalled with NoScript and uBlock Origin, the former of which you will either have to learn how to use or disable, depending on your wants for privacy. While it doesn’t include some of the anti-features of base Firefox, it is still based on Firefox so it will have similar performance for similar tasks.
Personally, I use Mullvad for most of my browsing, and Firefox for a few specific things (like staying logged into site long-term and such).
It’s available as a flatpak via Flathub for an easy installation, otherwise you can check https://mullvad.net/en/browser/linux for distro-specific installation instructions.