Apologies if you feel my response was lousy, I was responding directly to the previous reply of “please reconsider” to make it clear that this is unfortunately not possible.
As for rolling back, the link below (as shared by @shondreas already) will get you the last release in the 4.8.x series:
https://plexamp.plex.tv/plexamp.plex.tv/desktop/Plexamp-4.8.4.dmg
I’m not a macOS or Windows user, so unfortunately I can’t help too much with regards to preventing auto-updates, but my best hunch is perhaps modifying the permissions on the executable to disallow overwriting the existing one. Alternatively, perhaps a firewall rule to block the update checking endpoint might also work. That endpoint for macOS is:
https://plexamp.plex.tv/plexamp.plex.tv/desktop/latest-mac.yml
and for Windows, it’s:
