If you mean the Swift language version, we still use version 5.

Yes, I'm sure. This is my code (alternateIconName is a property in that method's class): func switchToAlternateIcon() async throws { guard let alternateIconName else { return } try await UIApplication.shared.setAlternateIconName(alternateIconName) }

Yes! That was it indeed. I read the instructions again and then realized, it needs to be an environment variable, not an argument. So for anybody else running into the same problem: Edit your scheme, go to the Arguments tab of the Run action and add a new Environment Variable, with the name DYLD_FALLBACK_LIBRARY_PATH and as value the correct path. (Even though the path may contain spaces, quotes are not needed)