No XR-4 Varjo Controllers: Update Varjo Unity XR SDK to 3.6.0 or newer in your project or, if you cannot do that, open SteamVR tray when running your application.
SteamVR Tracker role ‘Held in hand (any)’ does not work with Unity Input System.
High Definition Render Pipeline (HDRP)
Some built-in post process effects cause foveation area to be visible.
Directional light flare causes foveation area to be visible with HDRI sky.
Universal Render Pipeline (URP)
Unity 6.5 and newer has quad view support. (6.5.3f1 or newer for DX12)
Unity 6 LTS does not support quad view. Use stereo rendering.
Unity 6 depth is upside down.
Post processing causes foveation area to be visible.