Apple released iOS 13.6.1 on August 12, and as is traditional, Apple has now stopped signing iOS 13.6, making downgrading to that version of iOS no longer possible.
The iOS 13.6 update was a major update that offered new features for the Health and Apple News apps, as well as support for the new CarKey feature.
iOS 13.6.1 is a bug fix update addressing issues with data storage, thermal management, and exposure notifications. It is the only current publicly available version of iOS that can be installed on iPhones and iPads.
Apple is known to stop signing older versions of operating systems after it releases a public update, as part of an effort to encourage users to keep their devices’ operating systems up to date.