Experiencing the same issue. I'm on Xcode 15 beta 6. The same issue happened to me on beta 5. Upgrading to beta 6 worked a few days ago. However, I recently updated to the latest iOS 17 beta and now it's crashing again with the 'Symbol not found' error. Hope this gets fixed soon.

I'm on Xcode 15 beta 6 and simply removing the default values caused the model container to crash. Making the properties optional worked for me.

Replacing #Preview with the good old struct ContentView_Previews: PreviewProvider works for me. If y'all can't wait for the fix, this workaround should work. Thanks to the previous comment!