This post shows how to move your Plex data directory on systemd-based systems:
The specific example given shows how to tell the service to use a different Plex data directory than the default (the part showing “Environment” being set). It also shows how to change the user which the service runs as, though that may not be necessary in your case (see the information below regarding changing ownership of the directory).
I’d follow those directions rather than symlink’ing to /var/lib/plexmediaserver (though that should likely work as well).
Also, ensure that your new Plex data directory is owned by user and group plex. Something like sudo chown -R /home/jc/Plexmediaserver-var/ should work. Plex Media Server, by default, runs as user plex, so that user needs to be able to read/write/execute on that directory.
