Plex, PlexConnect and OpenPlex are running on Mac OS X 10.11.5 El Capitan. On May 16, 2016, Apple released Mac OS X 10.11.5 El Capitan (build number 15F34, ‘final release’). I positively tested it with an Apple TV 3 running on Apple TV 7.2.1 software. Find more about Mac OS X 10.11 El Capitan on Apple’s Website. I had not to re-install OpenPlex.
The OS X El Capitan 10.11.5 update improves the stability, compatibility, and security of your Mac.