R3 DumaOS 4 - Achieving Open NAT for P2P Hosting (GTA Online)

[ifell]

I am trying to achieve an Open NAT in GTA Online (PC) to host lobbies for achievements. Despite a perfect setup, the game consistently reports Moderate NAT.
 

 Netduma R3 Firmware: v4.0.540

Connection: Direct NBN Fiber (FTTP) to NTD (No ISP modem/Bridge mode issues)
Ports: All Rockstar-required ports (6672, 61455-61458 UDP, etc.) are manually forwarded. UPnP is disabled to avoid conflicts.

I cannot find a toggle for 'NAT Filtering: Open' or 'Endpoint Independent Mapping' in the DumaOS 4 interface. It appears the R3 is performing Symmetric or Address-Restricted NAT by default, which is preventing me from being the primary session host.