If a game is opened to LAN on linux, it is impossible to join, this is because Minecraft calls java.net.InetAddress.getLocalHost() to get the current IP, then broadcasts the server as being hosted on this IP. On windows this returns the LAN IP, a number like 192.168.X.Y, but on Linux, this returns 127.0.0.1 (which is what it should be returning, because that IS the local host. The windows java implementation is wrong.)