Zero fast. There is no energy being transferred to the people, they would plop out and push into each other as they are forced through.

If you blocked the stationary portal then the portal moving would essentially just be a wall, no one would go though.

This whole relative thing makes no sense, energy isn’t just created because it’s observed by someone else, the door is moving not the people so them sitting there won’t suddenly be catapulted going through a moving portal, where is that energy created?

Your wind question is confusing.

No energy is every transferred as a result of a portal

You fly in the air if you drop in one because you are carrying momentum downwards that suddenly translates to upwards

You are sat in the floor, a portal flies towards you. You are sat at the floor at the end, you had no momentum going in and no momentum going out

Why?

Where does the energy even come from?

A hole/portal doesn’t create or generate energy it just passes things through.

Just think of it as a hole across space because that is exactly what a portal is.