Here is what I found regarding passthrough over Oculus Link.
Passthrough over Link doesn't work and it doesn't seem to be a priority for Meta.
Meta allows it to work only in Unity editor, they will not allow apps in Oculus Store to use that feature.
But I will keep checking this functionality from time to time if anything changes.
https://developer.oculus.com/documentation/unity/unity-passthrough-over-link/
Important: You must enable the Developer Runtime Features and Passthrough over Meta Quest Link toggles in the Oculus PC app by clicking Settings > Beta. The Passthrough over Meta Quest Link toggle appears only when you enable the previous toggle.
Note: Passthrough over Meta Quest Link is a developer-only feature aimed at increasing your development speed by previewing your passthrough-enabled apps while still in development. That being said, the visual appearance and performance characteristics of the experience are slightly different between running over Meta Quest Link and running on an Meta Quest device.