Nowhere near as exciting as some of the other cool stuff in this thread but... I'm building https://trytalo.com - an open source self-hostable game backend. Talo makes it easy to drop in features like leaderboards, player stats, analytics and more into games. There's a Godot plugin, Unity package and Steamworks integration too.

I'm really early on in getting Talo out there so appreciate any feedback/criticism/roasting!