On distros like NixOS or Arch Linux, it is often easier just do get Mullvad Browser or Tor Browser off Flatpak, Nixpkgs, or the AUR. These repos however make very slight changes to the browser.
Like here in the Flatpak, it disables auto updates and add some custom branding to the browser. Or here for Nixpkgs and here for the AUR.
Tor browser has similar changes.