https://www.gamespot.com/articles/e3-2018-gamecube-controllers-work-in-super-smash-b/1100-6459724/

Super Smash Bros. Ultimate is the new Super Smash Bros. game for Nintendo Switch, and was announced during the E3 2018 Nintendo Direct. This means that Ultimate will likely be the primary version used in competitive play moving forward, and good news: It supports the GameCube controller.

While we had hands-on experience with Super Smash Bros. Ultimate using Nintendo Switch Pro Controllers, the game will be compatible with multiple styles of control. Here's what we know: