Yeah, AppleTV Channels is a “known” issue for Viacom (CBS AA and Showtime). They have inconsistent at best listings. Always best to go through direct app if possible until it gets sorted.I guess that is why these content quality discussions can go off the rails and get so confusing so quickly. Below is what the three (3) SHOWTIME series you listed show in the SHOWTIME channel in APPLE TV app on a Fire TV 4K Stick.
- The Chi (most recent season) on FTV4K it is the same. 4K Dolby VIsion.
- Ray Donovan (most recent season) on FTV4K all seven (7) seasons are in HD only.
- The Good Lord Bird on FTV4K is in 4K but no Dolby Vision.