I am using older commercial grade HP Prolient servers which are unable to run anything newer than CentOS 6.10. It appears that the newest Plex media server that will run on CentOS 6.10 is is 1.14.1.5488
If you can suggest another way that I can update to a newer version then please let me know. As it is I hate to simply discard these perfectly capable, and extremely robust severs due to discontinuation of backwards compatibility. I would image that you have many other users with the same issue.