GameCube controller support has come to the Nintendo Switch.
In the console’s latest system update, support for the classic controllers was added with no announcement. It still, however, needs the Wii U controller adapter.
Once you have the adapter and controllers plugged into the Switch’s dock, the controller is paired in the controller menu by pressing their L and R buttons.
I tried this on Mario Kart 8 Deluxe and everything worked as expected. Anyone who owns a GameCube controller will know that its buttons don’t match up exactly to a Nintendo Switch controller. For example, there’s no home button so you’ll need to swap controllers to get back to the main menu. For those who prefer the classic controller or just have extra laying around for multiplayer, it’s a great option.