I haven’t played minecraft on LAN, but according to the solutions from the Internet, the setup is quite simple. If your both laptops are connected to Beryl via lan cable or wifi (not guest wifi), then they will be on the same subnet, usually 192.168.8.0/24 if you have not changed the LAN settings.
You can see the IP address of your laptops through the command line, if this is a Windows system, a command will be ipconfig /all
Typical IP address for client of the Glynet routers is 192.168.8.(100-249) and the gateway is 192.168.8.1
You only need the IP addresses of your laptops. The rest is configured in the game.