You can check the about:policies#active page to see whether policies are active. Also see if this helps. https://support.mozilla.org/en-US/questions/1264369 What security software are you running?

i am running pop os lts and i reinstalled it and it still says that DisableAppUpdate is true

This is OK, because your updates are being managed by your package manager.

Some Linux distros are doing this with Firefox package builds. For example with Mint https://blog.linuxmint.com/?p=4259 though the page makes it sound like Firefox cannot do its own updates at all. Referring to this comment when they say "Firefox cannot handle its own updates. It doesn’t know how to check the repositories and doesn’t have admin privileges anyway. In Linux Mint this is the job of the Update Manager so Firefox is told not to handle updates."

The official Linux builds from say www.mozilla.org/firefox/all/ does get internal Firefox updates from Mozilla just fine much like the macOS and Windows builds. Just need to make sure the Firefox folder has read/write permissions for the user to do updates.