HDR is terrible
The fact that you can't turn it off system wide shows the macOS leadership is asleep at the wheel
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The fact that you can't turn it off system wide shows the macOS leadership is asleep at the wheel
You totally can, at least on Apple's XDR displays.
Just go to System Settings -> Displays -> Preset and change it from "Apple XDR Display (P3-1600 nits)" (or whatever) to "Internet & Web (sRGB)". You lose the ability to change screen brightness (I assume because you're locked to reference brightness), but HDR is fully off.