Mullvad Browser; Adding Bitwarden, Ublock Origin lists?

Yeah, unfortunately making changes like that will virtually always be detectable. If the default experience doesn’t work for you, using Arkenfox is a good alternative that will probably be better suited for cases like this.

I’m working on a browser fingerprinting guide that will hopefully be able to provide more insight into this stuff in the future, for now the Arkenfox Wiki on GitHub is a good resource for learning about this kind of thing, albeit a bit technical at times.