Hi there!
"MoltenVK.xcframework" folder is missing when building for iOS (appears red in Xcode's file structure).
It's there when original export templates are used (downloaded via editor).
If you unzip the export templates provided by Spine, you will notice that "ios.zip" doesn't have "MoltenVK.xcframework" folder inside 🤔
Workaround:
I've copied the missing folder to the export destination next to the ".xcodeproj" and the build went through 👌