Ok, so what you’re describing is exactly the issues almost everyone does have…except running the editor first. I always run multiplayer via command-line as it’s the only way to test it. When you get to the building of game assets, set up the network and 2 sessions in the editor and that works fine too.
Final testing - always command-line.
Just don’t try using the menu within Unreal as it just doesn’t work. This is not the implementation either. It seems to have been some regression in the engine. 5.3 is worse.