After the release of iOS 15.0.1, Apple has now stopped signing iOS 15.0, which was publicly released on September 20. Now, users will no longer be able to downgrade to iOS 15.0, if already updated to iOS 15.0.1.
Apple stops signing older versions of software update after the release of newer ones. This is to encourage users to keep their device running on the latest software version.
iOS 15.0.1 fixes an Apple Watch issue that was affecting iPhone 13 users. Users were unable to use a feature that allowed them to unlock their iPhone with an authenticated Apple Watch when wearing a mask.
The iOS update can be downloaded on all eligible devices from the Settings app. Users can tap on Settings, then go to General, and Software Update.