Last month I started hosting a TeamSpeak 6 server, and it’s been great.

Furi and Plate Up

It’s not quite self hosted, but Soulseek allows you to share share private directories with buddies. Soulseek might require a port forward.

Other than that, there are the many pasteboard solutions that have been mentioned. They’ll either require a port forward or reverse proxy (nginx etc.) to access outside the network though.

In addition to other’s comments, I think that we just have enough good games by now that a lot of people can find a game they enjoy enough to sink hundreds or thousands of hours into. Minecraft, Factorio, Satisfactory, Hollow Knight, Elden Ring, etc.