Librewolf is built on Gecko, people often accredit it as a "firefox fork".

Tor Browser seems cool, it's what I use on my phone whenever I have spare time to let it load before searching things which don't require a lot of bandwidth. I'll edit the above list.

Mullvad? Is that some kind of slur? I've never heard of that but searches say it's a VPN client. ¯\(ツ)/¯