With the Gold Edition of IsoMetro, the Grimesoft infrastructure allows you to host a game without running into port-forwarding headaches. A dedicated server is available (and due to being distributed as a Docker image, should also be fairly straightforward to set up on any platform), but you can also host an embedded server directly from the game. This is still the classic old-school city builder experience, just with the ability for multiple people to interact with the same world simultaneously.
Want to work on isolated cities and then connect them up naturally? You can do that!
Want to set up utility infrastructure while a friend builds roads in a new district? You can do that!
Want to randomly demolish important electrical lines and see how long it takes for everyone else in the server to notice that half the town has moved out because they didn't have power? Yep, you can do that too!
The multiplayer features are cross-platform both in terms of your operating system and the storefront you got the game from -- someone running Steam on Windows can join a world with someone who has IsoMetro through itch.io on Linux or Mac. If you want to, you can even allow unauthenticated users into servers (Free Edition players, who don't have access to the server browser but can still connect directly to server addresses).
Hopefully the experience is smooth for everyone, but in case you run into issues, we'll be keeping a closer eye on the Steam Forums, and especially our "Grimesoft Community" Discord: https://discord.gg/9y3exPTsV8
Thank you for your support of this project!