Has anyone tried installing Plex in a OSMC image for the streaming services plex offers?
Did you even attempt to use the search function?
https://discourse.osmc.tv/search?context=topic&context_id=17665&q=Plex&skip_context=true
Running Plex itself under OSMC is technically possible, as there is a Plex port for Pi based on an old version of OpenELEC.
I don’t think that many people are interested in it though, but it could certainly be run in OSMC if someone wanted to do this. There are also Kodi plugins to connect to a Plex backend.