The following is intended to serve as a centralized location for information on running a Plex client in OSMC. As issues or changes arise I’ll endeavor to update this post so people don’t have to go searching for the latest information. Feedback and contributions are welcome.
Currently there exists four Plex client add-ons for Kodi/OSMC. They are as follows…
Plex / Plex4Kodi / Plex for Kodi / "The official Plex add-on’
This is the add-on that is currently in Kodi’s repository listed under the name “Plex”. It had at one point been maintained by Plex but that had stopped years ago. This add-on has a similar look and function to Plex clients on other platforms. It had been maintained after that by someone else but as it stands at the time I’m writing this the add-on is broken and will not be fixed. Although it is possible to patch it manually to work, you would be better off installing the PlexMod add-on which is a successor to this one.
Plex / PlexMod for Kodi / PM4K
PlexMod is a fork of the original Plex add-on that has been updated with features and bug fixes that never made it to the original. If you want that Plex look, or had been running the original add-on and liked it, then this is the add-on that you want. It is not in Kodi’s repository but it can be installed easily by following the instructions provided over on Plex’s forum at the following url…
Composite
The Composite add-on allows you to browse a Plex server using a directory tree type of interface when you open the add-on, as well as gives the ability to add content from your Plex server as a regular video source for integration into a the regular Kodi library. This add-on can be found in Kodi’s repository.
PlexKodiConnect (PKC)
PKC seamlessly integrates your Plex library into Kodi’s regular library so you have in essence a Kodi front-end, with a Plex back-end. PKC can work quite well, but it should be noted that it may be a bit more prone to issues with updates than other options. More information and instructions for installing can be found on its Github page at the following url…
UPnP
As an alternative to running an add-on, one could enable the DLNA server in their Plex server and then use Kodi’s UPnP functions to browse and play from the Videos section of Kodi. More information on UPnP in Kodi can be found in their wiki at the following url…
https://kodi.wiki/view/UPnP
Plexamp Headless
I got it working some time back using some random instructions I found for Raspberry Pi OS IIRC and it seemed to work well.