The Application Support directory would have been on another drive if active. When not moved, the default is /var/lib/plexmediaserver ( on the OS partition )
This means you lost all your metadata when you reinstalled the OS.
Plex.tv doesn’t know the old server ID is gone, so it lists it.
The new server ID (instance) is, by default, created from the hostname. This is why you have what looks like a duplicate
It’s correctly stating the first instance of Quark isn’t available.
It looks like the second (new) instance of Quark doesn’t have libraries yet. True?
Look carefully at the Last Seen values.
The more recent one is the current Quark.
Personal note here: I put it in the /home partition and then make certain not to reformat /home partition when installing a new OS. This way, all my files and PMS survive OS changes.
But I still have the data at /srv/multimedia/plexmediaserver/Library/Application Support and I am still pointing to it now, is some meta data still at /var/lib/plexmediaserver even though I am pointing to /srv/multimedia/plexmediaserver/Library/Application Support ?
I did make one mistake. I started plex server before I put the override file in so once I realized that I hadn’t done that I stopped plex, put the file in, updated systemd, and restarted plex. I thought that would have made it all work but not so.