2021 Gen 2 and 2022 Gen 3 of Apple 4K TV support VP9 playback with YouTube app. You can see 4K HDR content on some YouTube videos. Setup your ATV4K to use 4K HDR by default not 4K Dolby Vision. If you have both Match Dynamic Range and Match Frame Rate enabled it will automatically switch from SDR to HDR to DV for 4K content for different streaming apps. YouTube doesn't support DV, but you still select 4K HDR as your default output.
You don't need to set your default output as 4K HDR, in fact I don't recommend it. Set it as 4K SDR, so your UI looks normal, and the YouTube App will push the output into 4K HDR when you have Match Dynamic Range to "On" as you're showing in your screenshot.2021 Gen 2 and 2022 Gen 3 of Apple 4K TV support VP9 playback with YouTube app. You can see 4K HDR content on some YouTube videos. Setup your ATV4K to use 4K HDR by default not 4K Dolby Vision. If you have both Match Dynamic Range and Match Frame Rate enabled it will automatically switch from SDR to HDR to DV for 4K content for different streaming apps. YouTube doesn't support DV, but you still select 4K HDR as your default output.
sample to try
Fake HDR is not good. When the Apple TV maps SDR to HDR it's the audio equivalent of boosting the bass and treble.
Matching Dynamic Range and Frame rate is just that, not outputting a forced 4K HDR output with altered color space because that is what the GUI is set to. Reminds me of how people used to think forced DV looked better on Oppo’s. I see the output switch from SDR to HDR to DV depending on video source. Using LG OLEDs also.
If you set the default Apple TV output to 4K HDR (or DV), then you are forcing a different color space for SDR content. This is regardless of your Match Content setting.
What I see when the screen saver or app interface is on is HDR Standard (user), then while playing 1080P content is ISF expert (dark room) against LG picture mode in use. That’s not HDR any more. Using tvOS 16.3 beta 1. Also checked 4K SDR YouTube video, still using ISF expert (dark room) also not HDR.
Then you have a unicorn LG OLED. Because every other one behaves like I described.
I have had two LG OLED TVs that act the same way. I have my default setting to 4K DolbyVision with Match Content & Frame Rate on. The LG OLED has always switched back to SDR when necessary as well as to HDR or DolbyVision when switching between different types of content. This is verified every time in the LG TV settings showing either the SDR Expert Select Mode I have or one of the other HDR or DV Select modes when such content is streaming. Maybe LG OLED TVs are the only ones that can do this with the Apple TV 4Ks, but they do switch automatically with no fake HDR or DV being used for SDR content.
Sony's TV's were a year behind LG when first supporting 4K dolby vision, in fact we all remember Dolby had to implement as second way for DV to work just because they were so special.
avgadgets.com
I have both a C7 and a C1, and neither of them will switch back to SDR, as long as the Apple TV video output is set on 4K HDR. I've observed the same behavior with friends and family LG + Apply TV 4K combos.
The "correct" behavior is what I'm describing.