I’m having an issue with built in Roku TV on my TCL 65r617 not playing Dolby Vision/HDR. My Apple TV running through HDMI correctly plays Dolby Vision on same apps, same content (toggling back and forth between Roku and Apple comparing content on AT&T TV and Netflix).
I have the same problem. My TCL 65s535 is not displaying Dolby vision at all! Did you manage to solve the issue??
I have the same t.v. HDR and Dolby work with my PlayStation including all the media apps on the PS... but apparently the built in Roku Apps on the TCL - 65S535 don't support it. I may return this T.V.... after doing some research I realized they have been doing this for years, so I am not feeling very confident they will update the built in apps to support HDR and Dolby.