I was able to set a static IP for my Xbox and open ports to get an open NAT type. I want to do the same with the PS5 to get NAT type 1. I have set a static IP and I have opened TCP: 1935,3478-3480 & UDP: 3074,3478-3479 ports on my router for this static IP. I tried restarting the PS5 and its still Type 2. I even restarted the router and the ports were indeed saved correctly but still type 2.
To go to the next step, I tried removing all the forwarded ports and set the IP i used for the PS5 for the DMZ setting. This essentially means no firewall for this system. Ran another network test on the PS5 and I still have NAT type 2. Is there a bug or something here since it is a new system? No matter what I do I am stuck with 2. I am pretty sure I am doing things right as I used the same port forwarding menu to get open nat with the Xbox.
It looks like it can be a big buggy at times but it appears to be a UI bug rather than a networking issue. Following all the steps you need to get an open NAT can sometimes take a while to register with the system, even though it is communicating with the internet without restrictions.
For anyone wondering, there is no drop down setting in the PS5 system settings to get an open NAT, you will need to open ports on the router and set a static IP to achieve it. Here is a guide with a video that will show you how to get an open NAT type on the PS5.