Most multiplayer games need this
From blueprints there seems to be no way to kick or remove player from the server without using a client side kick, which is not a correct way of doing it.
I currently know of no other solutions.
Yes… in unreal engine networking tutorial is kick setup. (That 24± parts video tutorial)
It is possible to create a client-side kick function as in those tutorials, but it would rely on the client accepting the kick rather then the server closing the connection and forcing the client out of the session.
It would be preferable to close the connection from the server side, but im not experienced enough with the source code to get into that at the moment.