Many thanks!
@AcWai, attached are screenshots of what I see. In my modem/router setup, all that's there is an option to enable or disable the NAT state. The second screenshot is of the Control Panel showing (limited) information about my connection.
View attachment 85702
View attachment 85703
Please search in Youtube "how to set up NAT forwarding with your router". There are a lot of videos on how to do it. All the videos show how to open a new menu to install the virtual servers. Can you ask your friends to see if they can set up NAT forwarding?
My old router is a TPLINK Archer C50. I am now using direct Ethernet connection in my house. I hope either you or your friends can set up multiplayer mode. I would like to play on-line with multiplayer.