That is not my external IP. I turned off NAT/PNP and set up port forwarding but get nothing. Additionally, through searching I thought the issue may be related to CGNAT, which I have requested the ISP to disable.
Most Aussie Broadband users on this forum have been able to disable CG-NAT by request as you’ve mentioned. Here’s an example from another ASUS/Aussie Broadband user: ARC not connecting to core on Asus RT-AC86U router - #17 by Jezep. You likely won’t even have to request a routable IPv4 address.
If the 504 timeout diagnostic persists after they’ve freed up your account, please let us know, and we’ll troubleshoot for another network issue.