Librewolf is an extremely hardened version of Firefox with all Mozilla tracking and shenanigans removed. Mullvad is also built on Firefox and is the TOR browser with Mullvad VPN instead of TOR. I have not used it, but Mullvad has an excellent reputation and track record and TOR browser is awesome if you use something like TAILS Linux to insure no other data leaks. It really depends on your threat model and what you’re trying to protect yourself against. 

 thank you 🙏