I see that iOS 18 has tinted app icons. Does anyone know what will happen if we choose not to provide a version of our icon for tinting?
Then the system will perform its own tinting if user asks for it, which may lead to a result you don't like.
But it is not required to provide a tinted version of app icon:
iOS and iPadOS support three stylistic variations for app icons: Light, Dark, and Tinted. You can create your own variations to ensure that each one looks exactly the way you way you want.
If you prefer, you can take advantage of the system’s automatically generated treatment that is applied to all app icons. It is crafted intelligently to preserve design intent and maintain legibility. This also helps maintain a consistent visual experience across the Home Screen.
https://developer.apple.com/documentation/xcode/configuring-your-app-icon