It'd be cool if you could easily publish multiplayers games to itch.io or similar websites from Godot or Unity and have automatic matchmaking: the first player to visit the game pages gets matched automatically with the next, and so on.

Is there anything like that?

You can't find the first one without the first one having static IP found from something in the page, which this thing solves using external services of developer choice, including commercial Supabase and Firebase systems. But the docs says it supports Bittorrent for that, so it's probably good.

I've been looking for this too!

I'd love to use an existing protocol to get (distributed?) user accounts and chat and stuff, and just build my game as a plugin for that. Or something.

I used Trystero in exactly this way for https://www.farmhand.life/!