All major platforms (Windows, Linux, Mac, Android, iOS/iPadOS) allow apps to have multiple icons, letting users choose which one should be displayed on desktop/home screen/in app menu. The icons to choose from could include legacy icons, Firefox Preview icon, recently released Halloween icons and more.
Similar, platform specific ideas were proposed before (iOS, desktop), but without much success. This proposal attempts to streamline the voting by covering all platforms at once.
Icon examples: