This may be a “no duh” post, but recently I turned off HDR on my 2nd gen 4K Apple TV. I’m running a TCL 65” 4 series. It has hdr 10 but it’s not FALD. I always had HDR on because it felt like that gave me the best image. I was shocked when I turned it off and got better color accuracy and better contrast out of the tv. Feels like a gimme that you shouldn’t use HDR without FALD or Mini LED, but I am much happier with the setup now
On my TLC I found the brightness of some HDR content is actually dimmer then when set to SDR, so I just have HDR off and it’s way way better. I’m using a 4K 3rd gen and the color balance setting.