If it can be of any help here's the error I had in the logs when the game kept crashing:
System.Exception: UPnP could not forward ANY port in the 12346-12356 range at TheCheaps.NetworkClient..ctor(IPAddress ip, Int32 server_port, Boolean use_upnp) in /home/runner/work/MGJam2021/MGJam2021/Code/TheCheaps/NetworkClient.cs:line 69