Nvidia Shield TV Pro 2019 is a great Box with 8.2.3 or 9.2.0.
Plex has actually some problems, but good working will this Versions:
Plex Player 10.22
And Plex Server 1.40.4.8679
Later Server Version made problem for some user. You will found here many problem threads with server 1.40.5.8921 or newer.
