This project is the lobby system from the Bomberman demo combined with the lan discovery plugin made to be plug-and-play to aid in learning Godot's networking capabilities
If you would like to test this out there is a compiled demo on Itch
To use this in your own projects you just need to copy the lobby file and the plugin file into your project's file, then make gamestate.gd a singleton and enable the plugin. You can then change the scene gamestate.gd instances in the start game function with your project's main scene