Hi @rossfrancis497 . Is your current router next to the NTD, or have you used one if the ethernet ports to place the router elsewhere in the house?
If together, connect second router as access point to main router.
If not together, can you run a cable from main router to the back of your house?
Or, maybe a wifi extender.
I think the UNI-D2 port is for a separate NBN connection, not an extension of yours.