On the Plex website https://www.plex.tv/apps/computer/kodi/#
With the Plex for Kodi add-on, you get the Kodi experience for your big screen, powered by Plex Media Server, and enabling you to organize and access your beautiful media on any device, anywhere, anytime.
Stream all of your media to all your devices, anytime, anywhere, with the same beautiful experience on all of them. (iOS, Android, and Windows apps require a one-time unlock fee for full playback if you do not have a Plex Pass.)
I can't for the life of me get the Plex for Kodi player to show up on my list of player targets (from any device). I am a Plex Pass member.
How can I get this working? All ports are open on my local area network (other players work fine)
Arch Linux (mentioned because while the question is independent of the operating system, perhaps the answer will not be.)