Plex usually offers new apps and features only for paying Plex Pass subscribers and then, after some time, apps get released to everyone for free. That time has come for owners of select Smart TVs, including those running Android TV.
Plex free on more devices
Plex has been very active in the past few months. The company has released a free app for Roku & Xbox 360, updates for PS3 and PS4 and an entirely new player for the PC with 4K support.

The Plex app is now also free to download and use on Smart TVs. Compatible devices include LG’s 2013 Netcast TVs and 2014+2015 webOS TVs, Sony’s 2013 and 2014 Smart TVs, Toshiba’s Smart TVs and 2013+ Vizio TVs. A full list is available here.
The media player app is also free on devices running Android TV such as Sony and Philips’ 2015 TVs as well as media player boxes such as Nvidia Shield and Nexus Player.
The Plex app was already free on Roku, Tivo, Chromecast, and Xbox 360.
The Plex app for the new Apple TV on the other hand has been delayed. Plex had hoped to release it in time for the Apple TV launch, but Apple rejected the first version due to some issue.