Am having the same issue. Tried deleting both 13.4.1 and 14b3, all related caches, clean project, delete all in Library/Developer/Xcode/*, reinstalling, rebooting in-between and I'm still unable to open any .xib/.storyboard. xcode-select -p is showing the correct path as well... Incredibly frustrating this.

It seems showing AppIcon's within UIImage(named: String) is deprecated. See the release notes for Xcode 16 beta 5: If UIImage(named:) was called with the name of an app icon, it would previously return an undefined image of the icon set, without any masking or shadowing applied. On iOS 18, it now returns nil. To display an icon within the app itself, add the desired image to the asset catalog as an image set. (130491812) (FB14052579)