I really wish the developer would either create server hosting software that allows us to host our own lobbies and games without the need to connect to a server provided by some cloud provider, or at least open source the server technology for us to be able to create our own server hosting software.
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I'm using Photon PUN, the only proprietary server used for the game is the authentication server. The game "server" is mainly used by the game just a relay for the clients to communicate with the host.
It's possible to make your own Photon PUN "server" / subscription (the free tier is 20 users at once), but I didn't expose a way to change out the server ID that the game tries to connect to. I'll consider adding a way to change that in some config in the next update, but at the same time, this spike in players isn't going to last forever. In about a week it'll be easier to get in.