MacOS Big Sur Icon
I'm not sure where exactly I should put this, but I recreated the icon for MuseScore using the official MacOS Big Sur icon templates by Apple to fit the look of the new Big Sur icons.
I used the current MuseScore 3 icon's colors to recreate the gradient and fit it in the icon template, and extracted the text from the flat logo (the logos here have no gradient so I could use "color to alpha" cleanly): https://musescore.org/en/about/logos-and-graphics
The default drop shadow is part of the template so I didn't have to do any work with that.
I've uploaded the png here so anyone can use it and maybe it can make it into an official build in the future.
I can't upload .icns files so, if anyone wants to use this, you need to convert it to that format for MacOS to recognize it.