I have exact same problem. I was able identify that the database is now located at /data/plexmediaserver/Application Support/Plex Media Server/Plug-in Support/Databases/.
I want to optimize the plex database to increase default_cache_size. For this i need to use sqlite and have the service plexmediaserver stopped. the problem is that when i stop the service, the whole plexmediaserver folder disappears from data forlder…
No, nothing yet. I’m actually looking to install external plugins like the “Metadata agents for exported XBMC library”. I don’t have the drive with me know but will check soon and report back, maybe I missed something.