
You can just use port forwarding, and use the broadcast_ips (if I’m not misremembering the name) setting on your friend’s config to try to connect to your public IP.
If you are on windows, the experimental version of the emulator has an overlay (a bit like steam) that allows you to see if you are detecting the other player a bit more easily, and to invite them with just a click (like on steam).
Since it is then direct connection you shouldn’t have any overhead lag unlike with hamachi and the like.

Goldberg emulator. Open source, you put it to replace steam’s api dll, and you can configure it for multiplayer. So you just need clean steam files of the game, and an properly configured goldberg, and the multiplayer works.
Configuration can be a bit of a hassle I guess, but less than editing the source of the game and compiling it.
Yeah no