Do you mean the ASUS DSL-AC68U? If yes, based on the specification that it is a VDSL modem/router.
This means that it is compatible with the TPG NBN FTTN service.
In the configuration of a third party device, you need to make sure that you use the VLAN ID to 2, PPPoE with the correct TPG username and password.
Also, the bundled VoIP service won't work on a third party device as the settings is embedded in the firmware of the supplied modem/router.