Thank you so so much! This saved my life on UE 5.0.3 when none of the other suggestions (disabling/enabling Mobile HDR, Instanced Stereo, OpenXR plugin, MetaXR plugin)!
For posterity, I switched the anti-aliasing to FXAA.
Hoping someone else can explain what’s going on or if MSAA has some bugs for now because MSAA has always recommended in UE docs like this XR Best Practices in Unreal Engine | Unreal Engine 5.0 Documentation