Free for macOS 11 and Xcode 13
"Iconset Kit is a simple icon generating tool designed to help you create app icons for macOS, iOS & watchOS. It is easy to use and intuitive so anyone can manage it with ease. The utility supports importing images in most popular formats: PNG, JPG, JPEG, and TIFF.
The application has a clear-cut and modern-looking interface. Without any preferences to tailor, the icon generating process can be controlled conveniently from the main window. The tool can create both retina and non-retina assets.
To sum up, Iconset Kit offers a straightforward icon generation approach so you can get your app icons fast and without hassle. Using the application is very easy. It isn't time consuming, allowing you to concentrate on other important activities."