If you mean can it replace the Optus supplied Sagemcom modem then no. FTTN requires a VDSL2 modem and the GT-AX11000 is only a router not a modem/router.
Appreciate your quick reply.
Can you please recommend one that will give me the best possible speed and wifi range? I also plug in my Mac using Ethernet too as I do a lot of webinar hosting.
I don't follow router/modem scene so don't have a specific recommendation that I can give, but you should aim for one that has a Broadcom Chipset modem as those give the best line syncing for FTTN/FTTB.
Your best bet is to check out the Whirlpool Modems/Routers forum.