https://www.gamespot.com/articles/mario-kart-8-for-switch-can-now-be-played-with-a-n/1100-6460024/

Nintendo has rolled out a new update for Mario Kart 8 Deluxe on Switch. On top of resolving a small handful of bugs, the patch introduces an unexpected new feature to the mascot racer: Toy-Con compatibility.

After installing the update, players will be able to use the Motorbike Toy-Con from the Nintendo Labo Variety Kit to play Mario Kart 8 Deluxe. The cardboard controller can be selected from the new Toy-Con icon that appears along the bottom of the game's main menu screen, and it works with all of the game's modes and vehicles. Provided you have four Toy-Cons laying around, up to four players can play together using the new control method locally.