There is no current support for either Plex or Jellyfin.
That was always planned, but there hasn't been prioritization to complete the drivers.
Jellyfin was to be first, followed by Plex (due to it's popularity).
I control Plex through my Nvidia Shield, which of course is controlled by the Smart Remote. This work around does it for me. If I am going to do Plex server type operations, I do it on my PC anyway.