I have an old BT home hub 5A used as a switch ,does anyone know if it supports a usb to ethernet adapter to give me an extra port
To be honest, I don’t rightly know, but I would be surprised if that worked.
You can buy a 5-port switch on Amazon for a tenner and an 8-port for under £15.
For that to work, the HomeHub 5A would need to have the ethernet adapter's driver built in to its firmware, (unlikely, but not impossible).
.