So we're trusting Tor but not Mullvad who collaborated with the Tor Project [0] to create this browser?

... developed in a collaboration between Mullvad VPN and the Tor Project

Who's behind Librewolf and Ungoogled Chromium that we should trust them over Mullvad?

Even Librewolf recommends you use Tor [1].

Can I use LibreWolf with Tor?

Please don't.

The Tor network is designed to give you complete anonymity, but it can be compromised if you use it with any browser other than the Tor Browser. If you want anonymity, download the Tor Browser.

They're all open source projects, how do you define who should/shouldn't be trusted? Seems rather reactionary to discredit Mullvad without any evidence when the alternatives provided suffer the same issue - who's behind the project and how do you establish trust?

Lastly, Ungoogled Chromium provides almost no privacy enhancing features by default [2], so how could this be a recommended as a privacy preserving browser?

ungoogled-chromium features tweaks to enhance privacy, control, and transparency. However, almost all of these features must be manually activated or enabled.

Lets discuss real alternatives and real issues, not jump to conclusions and throw everything out because it's not "perfect"

"Don't let perfect be the enemy of good" and all that.

[0] https://mullvad.net/en/browser

[1] https://librewolf.net/docs/faq/#can-i-use-librewolf-with-tor

[2] https://github.com/ungoogled-software/ungoogled-chromium#objectives