I've been trying to play Hardcore mode together with my brother over LAN, but i can't seem to figure out how to turn it on, can someone help me with that?
When you create a new world the Gamemode selector under the Name box has Hardcore as an option.
I believe that would apply to all players, the Wiki claims the setting applies to the world not to individual players.
Alternatively the Hardcore tag should be settable later with an NBT editor but I have no experience using one.
You should be able to broadcast to LAN if you go into your hardcore world first and press the escape key on your keyboard.
You then should be able to see 'Open to LAN' just above the 'Save and Quit to Title' button.
wait you can play lan on hardcore?
Create a new hardcore singleplayer server and open it to LAN. Btw, hardcore is a gamemode.