Following the release of iOS 15.0.1 on October 1, Apple has stopped signing iOS 15.0, the iOS version previously publicly released on September 20.
With iOS 15.0 no longer being signed, if you have already updated to iOS 15.0.1, it is impossible to downgrade to the former.
Apple also stopped signing iOS 14.8 last week, which means that iOS 15.0.1 is currently the only publicly available version of iOS. Those who have already upgraded to iOS 15 cannot downgrade to iOS 14.
iOS 15.0 marks an important version update, introducing focus mode, real-time text, improvements to Siri on the device, iCloud+, Safari, and more details.
iOS 15.0.1 fixed a bug that prevented the certified Apple Watch from being used to unlock the iPhone 13 model while wearing a mask.
It also fixes a bug that could cause the “Settings” app to incorrectly display a storage full alert, and fixes a bug in the audio meditation for Fitness+ users.