I checked my libraries and they are all using the modern agent, explicit content disabled.
On the Plex app for AppleTV, most cast have no pictures, and Plex is unable to find anything in my library or elsewhere for most of them.
For the same shows/movies, the Plex Experience Preview app for tvOS (2025.19.0 — which is the latest available before builds were removed by Plex recently) displays everything perfectly: pictures for casts, related content, etc.
I still suspect there is something off with the regular build of the Plex app for AppleTV.
