LG Smart TV Plex client app not seeing any free stream movies (vod)

To find the correct WebOS and Plex app for LG, go to Plex settings/about or Plex server settings/ authorised Devices.

WebOS should be 3.5 for 2017 models.

As for Plex LG app updates there have be numerous updates that occur when starting up your TV. What your seeing in the LG store is an app loader dated August 2019.

Unfortunately WebOS 3.5 does not support VOD from plex.