First of all we have an extra option for local multiplayer, specifically within the 'Local' mode where you connect with other owners of the game that have their Switch in the same room. The 'Arena' mode has been added to this section; unlike 'Party' which mimics the random mix of matches in the online equivalent, Arena adds the Spectator feature promised during E3. Up to four systems can join the lobby locally and you then take part in one-on-one matches while the other two players spectate. You can use a splitscreen to swap between four viewpoints when spectating.
The other major addition is LAN play. To access this you press the left stick and then hit L+R on the main menu screen, which will prompt the Local menu to change to LAN Play. It offers the same modes as wireless local (Party and the new Arena mode) but with that improved stability that wired LAN can offer; that could certainly be useful when running tournaments, especially with the Arena option and the spectating option.
Let us know what you think of these additions. The next major update is set to add Max Brass to the roster in the coming weeks.