UIAppSupportsHDR
A Boolean value that indicates whether the app supports HDR mode on Apple TV 4K.
Discussion
If you set this key to YES, Apple TV 4K remains in HDR mode when launching the app. If you set this key to NO, Apple TV switches to SDR mode before launching the app, and switches back to HDR mode after the app resigns. The default value for this key is YES.
On Apple TV 4K, HDR mode uses the GPU to compose the content that appears onscreen. GPU-bound apps, such as games, can access more of the GPU by setting this key to NO. When an app switches between HDR and SDR modes, color flashing might appear onscreen, so only opt out when absolutely necessary.