
iOS 16 hasn't been the smoothest one of the lot, and we're now nearing the end of the update cycle on it. Apple recently pushed out iOS 16.4.1, with a few bug fixes, and the update is now seeding out to iPhones all over the world. Following the update, Apple has stopped signing the older iOS 16.3.1.
At the time of writing, iOS 16.4, and iOS 16.5 beta is still available for downgrade, but iOS 16.3.1 has become the latest software version that Apple has stopped signing. Apple is known to stop signing older versions of iOS as newer ones are released.