PS5 Co-Op with NAT type 3

So I just wanted to play coop with a friend but seems like we can’t join our lobbies since I’ve got NAT-type 3 and he’s on type 2. The thing is, my WiFi is with a gigacube which means it’s through a mobile data card which puts me into NAT-type 3. I‘ve googled a lot and seems like I cannot change this to 2 without using a vpn which isn’t an option for now.

I stumbled across a Reddit post here which said that type 3 can only play with other players in type 3, so here’s the question: how can my friend change his settings to move from NAT-type 2 to type 3? I haven’t found any solution on the internet since nobody wants to do this by choice (which I can understand)

Any help is very appreciated :)