Apple has just released the first public beta of iOS 15.4 on iPhone and iPadOS 15.4 on iPad. It comes 24 hours after the developer release.
First public beta available for iOS 15.4
One of the two main new features of iOS 15.4 is Universal Control. Now all you need is a single keyboard with mouse or trackpad to control a Mac and an iPad, or even several. Move the cursor from your Mac to your iPad. Type text on your Mac and see it appear on your iPad. And you can even drag content from one Mac to another. The other big new feature is the ability to use Face ID to unlock your iPhone while wearing a mask. This requires having at least an iPhone 12.
If your device is set up to receive public betas, go to Settings > General > Software Update. You will be able to download and then install the first public beta of iOS 15.4. If, on the other hand, your device is not configured and you want to test the public betas, go to beta.apple.com, log in with your Apple account and let yourself be guided. This includes uploading a profile to switch your device to the betas channel.
Apple does not yet give a release date for the final version of iOS 15.4. So we have to wait a few more weeks.