My server I running on Windows 10 pro and I have a smart TV and two desktops that work perfectly.
My Rasplex ( latest version ) only plays some media files. The Rest says the item is not available make sure the drive is mounted. My google searches have not really helped so far.
I have reloaded the Rasberi Pie and restarted the server but still.
That is an add-in for Kodi which provides Kodi with the ability to play content from a Plex server.
LibreElec is, basically, a minimalistic operating system (based on Linux) with Kodi on top of it. So very similar to what Rasplex was. It only needs the bability to access your Plex server. And that is what the Plex4Kodi add.in provides.
You can install the add-in right from inside of Kodi. (the device needs internet connection for that)
There is no need to add anything to your Plex server.