Here are some cool examples I was looking at:
https://github.com/zardoy/minecraft-web-client — Minecraft in your browser, complete with connections to servers.
https://github.com/inolen/quakejs — quake 3 in your browser, has multiplayer as well.
Any other good examples? or good lists?
I tried myself to look for self hosted family multiplayer games with no luck, I found this one that looks very good Rahoot.
I vibe coded a Parcheesi for local playing with my family, we have a lot of fun with that.