Fingers crossed for a Gamecube adapter for switch. They did it for the Wii U they can do it for this hopefully.
Do you mean the adapter that let's you use Gamecube controllers? You can use the one for the Wii U on Switch, that's what I do.
I only use it for Smash though because GC controllers don't have gyro and I love me some gyro, especially in Zelda. But yeah, I have like 16 functioning GC controllers ill use those if I have to.