If you're having to screw with defaults right out-of-the-box, with Ubuntu, you may as well just use Debian. Basically its whole value-prop was originally "Debian, but with obviously-correct defaults for most desktop users".

Even after you add the Firefox repository, installing Firefox from APT is not as simple as "sudo apt install firefox". That command would still install the Snap version of Firefox. You have to figure out how to force APT to pick the "firefox" package from the new repository rather than from the default Ubuntu repositories.