Today Apple stopped signing iOS 14.7 after releasing iOS 14.7.1 to the public. This makes it impossible to downgrade to iOS 14.7 for users that updated their devices to iOS 15 beta or even iOS 14.7.1
On 26 July, iOS 14.7.1 released a bug fix to prevent users from unlocking an Apple Watch using the iPhone Touch ID. The update also corrects a hacker-exploited security vulnerability.
Apple is currently running iOS 15 beta to both the public and developers for an autumn release.