Apple Stops Signing iOS 15.5 Following iOS 15.6 Release, Downgrading No Longer Possible
Following the release of iOS 15.6 last Wednesday, Apple has ceased signing iOS 15.5, the previous version that was available in mid-May.
Since iOS 15.5 is no longer being signed, it is not possible to downgrade to that version of iOS after installing iOS 15.6.
Apple routinely stops signing older versions of software updates after new releases come out in order to encourage customers to keep their operating systems up to date–
iOS 15.5 was a relatively small-scale update, with improvements to Apple Cash in the Wallet app and a new setting that lets Podcasts users limit the number of episodes stored
It also addressed some small bugs, including an issue that could cause the Settings app to continue to display that device storage is full even when it's not.
This upgrade is rather small, as Apple's iOS 15.6 release notes show. Given that this version's timeline is coming to an end, this is completely expected.
Sports fans who use the Apple TV app to watch games could find the extra playback control choices useful. Other than that, iOS 15.6 doesn't offer much cause for excitement.
Installing the iOS 16 beta may be a good idea if you're hoping for significant improvements. However, it is currently not very stable.