https://wccftech.com/download-and-install-ios-15-4-and-ipados-15-4-without-a-developer-account/

Apple's latest iOS 15.4 and iPadOS 15.4 beta updates for iPhone and iPad, complete with Universal Control is now available for public beta testers.

After an insanely long wait, Apple's Universal Control feature is finally available to test out as long as you are enrolled in Apple's paid Developer Program. Thankfully though, iOS 15.4, iPadOS 15.4 and macOS Monterey 12.3, which supports Universal Control is now available for free to test out today. All you need to do is sign up your device to Apple's Beta Software Program.