Focusrite Control for the 3rd Generation audio interfaces isn’t quite up-to-date with M1/Big Sur, so you may have issues with certain Focusrite interfaces, and in order to use the updated firmware, you have to be able to use Focusrite Control. Although the interface would work with MainStage and Sunday Keys, the headphone jack may not work.
One workaround is to download the Focusrite Control app onto an older MacBook, hook up the interface, and do the firmware update from there, and then it should be working properly.