Librewolf is debranded Firefox to remove all the sponsored crap that Firefox inserted: Pocket, Hello, new tab recommendations, default google search, etc.
Mullvad browser exists to advertise a VPN.
I would not recommend the latter in lieu of the former.
Mullvad browser certainly exists in part to advertise a VPN, but offers more privacy protections than Librewolf.
See this response from the mullvad-browser developer on exactly this:
> There are two main reasons, one which you preemptively answered:
> - the privacy model is about having a same fingerprint per platform for Mullvad Browser users, so you're not uniquely identifiable (which will be the case by following privacy hardening guides)
> - it is much easier to recommend to user a browser pre-configured for an optimal privacy: some users will want to tinker, but if you don't have the time or knowledge, it's hard to do the right thing
> There are also more differences than "just a fork of Firefox", I encourage you to read the following page which goes more into the details: https://mullvad.net/en/browser/hard-facts
So as much as I despise companies putting low effort into software rebrands that offer no value, all the facts point towards that very much not being the case here.
Edit: However https://privacytests.org/ shows mullvad-vpn and librewolf as being very similar wrt privacy.
