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!

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.

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.