Welcome to the community!
If the modem/router support NBN connection it should work however you will need to consider the type of NBN service you have.
If you are going to use it as the main modem/router for your NBN FTTN service, you need to make sure that it will be configured with VLAN ID 2 and the connection type is PPPoE that will require your TPG username and password.
NOTE: The VoIP phone will not work on any Third party device.
You may also find this threads helpful.
You may contact ASUS support for further guidance with their modem.