I quickly created a version of the existing app icon with a transparent background, which should allow for the system to apply a gradient background by default. Please feel free to use it as is or to apply any modifications to it (could be used for the tinted icon too).
With iOS 18, apps can have dark icons: https://developer.apple.com/design/human-interface-guidelines/app-icons#Platform-considerations
I quickly created a version of the existing app icon with a transparent background, which should allow for the system to apply a gradient background by default. Please feel free to use it as is or to apply any modifications to it (could be used for the tinted icon too).