Nintendo released the latest update for the Nintendo Switch game the ARMS. With the new 1.1.0 version you can enjoy the Arena mode and the LAN gameplay mode.
To play with the LAN mode, on the Top Menu, click and hold the Left Stick and then press L+R to switch between Local and LAN Play.

The Arena mode is focusing on serious 1-on-1 matches and can be played via Friends, Local, or LAN Play. Up to 4 players can be in the arena, and players not currently fighting watch as spectators.