Thanks for your help, @Josh Steinberg . The way Apple has implemented HDR with the AppleTV really is poorly done. When I set up the new TV and switched the input to it, a menu popped up stating an HDR TV had been sensed, and did I want to enable HDR on the ATV? Of course I do. Why wouldn't I? I clicked "Enable". The thing is it switches the overall output setting to HDR for everything. It SHOULD set the output to 4K SDR in that setting, and enable "Match Source" in the second setting that I didn't even know existed.
Also, I got looking at the specs of this TV. As I suspected, it can't really do HDR, though it can process it. I compared it to a Samsung QLED and an LG OLED, which can truly do HDR. The test results with those had local, HDR output capability that was significantly higher than their regular output. The TCL was no different between standard and HDR. So, it can process HDR, but it's just remapping the dynamic range within it's regular range. Still, the picture is very good, especially the streamed DV sample clips I found. I can't believe this TV was barely over $200.
Also, I got looking at the specs of this TV. As I suspected, it can't really do HDR, though it can process it. I compared it to a Samsung QLED and an LG OLED, which can truly do HDR. The test results with those had local, HDR output capability that was significantly higher than their regular output. The TCL was no different between standard and HDR. So, it can process HDR, but it's just remapping the dynamic range within it's regular range. Still, the picture is very good, especially the streamed DV sample clips I found. I can't believe this TV was barely over $200.