Colliders Behind The Portal

Players or objects can only pass through a portal if there is no collider immediately behind the portal, such as a wall or floor, which would impede traveling through the portal surface.

The simplest way to handle that is to manually build the colliders of your wall or floor in such a way that there's no collider behind the portal. Of course, that only works if the portal does not move.

A more advanced method is to have colliders behind the portal turn off when the player is inside the portal trigger, on the front-side of the portal. However, implementing this would require logic specific to your world and your use case, so I have not included that in the prefab. I may try to implement some "built-in" solution for this eventually, but for now, you're on your own!