Turns out it isn't supported in PolySpatial yet: Unity Docs
EarthAdam
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Found a place to Upvote this in Unity's roadmap: https://portal.productboard.com/unity/77-unity-visionos-roadmap/tabs/272-mr-immersive-features under "Improved Graphics Support".
I tried all of these steps. Even when my MacBook is displaying to the VisionPro. just ran software updates on both and that seems to have worked