I have a slightly unusual setup- our ONT is in the garage and I use a powerline adapter to bring the UFB network to our Ftitzbox 7490, which is downstairs in the living room and on an island wall that does not touch any other wall. It goes:

UFB>ONT>Powerline>Router>Wifi/LAN

We have recently put an Xbox in the study which is upstairs and far away from the wifi, and not receiving much signal due to floors, walls and cupboards. Unfortunately, we can't put structured cabling in anywhere.

My question- can I use a single additional powerline adapter to bring wired LAN from the router to the study? Or is the existing adapter on the wrong side of the router? I don't want to trail another network cable to a fourth adapter as the router is not near any other power circuits I can use. I assume there is nothing on the ONT itself I can use either.

Alternately, I have an old N-class router. Could I use that as a bridge, would that be worth my time?

Otherwise, what wifi range extender would be good bang for buck here?

Thanks in advance

Jon