Using Xcode (e.g. version 16.1) and Gimp:

• If no (default) asset catalog exists in the iOS project, create one with Xcode: File -> New -> File from Template... -> (Resource) Asset Catalog -> Next -> (Save as: Assets.xcassets) Create

• Create a graphics file, e.g. AppIcon.png of (NB!) 1024 x 1024 pixels. Starting e.g. from an .svg file, open it in Gimp with the required dimensions, then export it as a .png. (A Google Playstore 512 x 512 .png file will not be accepted.)

• In Xcode, select Assets.xassets (maybe the one created in the first step) in the Project Navigator. Then select AppIcon in the tab on the right, and double click on the block labelled 'Any Appearance'. Use the file picker that appears, to find and accept the file AppIcon.png created in the second step.

• Launch the app from Xcode on a simulator or device with the 'Start the active scheme' arrow button. Wait for the debugger to attach to the target (done when the message at the top right says 'Running [app] on [target]'), then stop the app with the block button to the left of the arrow button.

Check on the simulator or device to ensure that the default iOS app icon has been replaced with the one created in the second step.