Let me know in the discord about any networking discoveries or disappointments -- I've been thinking of writing a network library and covering all the basic stuff like player joining/leaving/messaging but in a way that's more palatable to Ebitengine's design.
So I did write/use a network library for all the network stuff, and I have just implemented support for KCP-GO/UDP implementing this change on the game will only require one line change, ujuuu. Only issue I have right now is, I'm not sure that if I upgrade the server it will be backwards compatible with what is running right now, so I'll probably update after the jam is over. And will upload the change here on itch.io. Nice thing is that you'll be able to use either UDP or WebSocket and clients can coexist between each others. This is the library last commit is the UDP support, tested with small cmd chat client.