We use a "launch storyboard" for iOS to configure your app's launch images. This is to simplify launch image support across a wide range of device sizes and resolutions, and is also required by iOS to support the larger iPad devices at native resolutions.
However, some clients prefer to specify a full-screen launch image for each device type.
This is still possible, but requires making a few edits to the iOS source code directly.
Here are the steps!
1. Open iOS source code in Xcode, and clear out the "Launch Screen File" under General section.
2. Open Images.xcassets and select App Icons & Launch Images -> New iOS Launch Image
3. Specify individual images for each device type, following the resolution guidelines at https://developer.apple.com/design/human-interface-guidelines/ios/icons-and-images/launch-screen/
Please let us know if you have any questions!