The black screen issue that you’re experiencing when using Meta Quest2 in Unreal Engine 5.1 with MobileMultiView turned off is a known issue. This happens because MobileMultiView is required to properly render stereo images for VR devices like the Meta Quest2. Turning off MobileMultiView means that only one eye is being rendered, which causes the black screen issue in the other eye.
Regarding the MobileHDR issue, you’re correct that MobileHDR and MobileMultiView cannot be turned on at the same time in Unreal Engine. This is because MobileHDR requires rendering with multiple render targets, which is incompatible with the single render target required for MobileMultiView.
Unfortunately, there is no way to turn off MobileMultiView on the Meta Quest2 without encountering the black screen issue you described. The best solution would be to use MobileMultiView and turn off MobileHDR, or vice versa, depending on the specific requirements of your project.