No Xcode support for iOS 12.3

I find a solution to fix this problem.

You should make a folder named 12.3 (... what is written in your error message) in Program/Xcode-beta/Contents/Developer/Platforms/iPhoneOS.platforms/DeviceSupport/ and copy the files from 12.2 in there.

Now you can run your apps on iPhones with iOS 12.3.

Any update on The IOS 12.3 Beta Developer Disk Image? The official Debugging File for iOS 12.3 is not available. You can try the following method to let Xcode support debugging iOS 12.3 devices.
1. Go to the folder /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/DeviceSupport
2. Create a folder named "12.3".
3. Copy the "12.2" file to the "12.3" folder.