So I've been told by someone that they've tried every buttons to use the Red/Blue Star powerup and apparently none of them are adjusted to the powerup button. The PS4/PS5 controllers and the GameSir G8 controller (the 3rd party controller I'm currently using more) all don't have that kind of issue, the attack button is R2 (For Playstation controllers), RT (from my Gamesir controller). For Nintendo Switch Pro Controller it should be the ZR button but this one for some reason isn't adjusted yet.
#Nintendo Switch Pro Controller issues
tame pumice
dense drum
I can attest to this. Every button works minus the the attack power up button. ZR would be the equivalent if it's R2 for Playstation controllers