I am having the same problem, but only with the iOS 26 Beta 5 Simulator. The other simulators install fine. I have restarted Xcode and even reinstalled the Beta Universal Simulator and cleared cache, but all times when I attempt to get the simulator I instantly get the message "IOS 26.0 Universal Simulator (23A5308g) Failed - Download failed"

I am having the same problem. My widgets stopped working with Xcode 16 and iOS 18 both on the simulator and on actual devices. I also am using UserDefaults to pass data, but the data is not passed but it was under previous Xcode versions. The app will still launch from the widget, but the widget data is missing.