iOS 10.3.3 can be installed on iPhone 6s!
Apple is stopping signing previous versions of iOS so that users will not be able to return to their old versions a few weeks after each new iOS update . Apple follows a policy this way with the most recent version being the safest and stable version.
However, there are also users who want to jailbreak by turning over old versions of the user . For this reason, Apple is completely shutting down. It's an interesting situation for the iPhone 6s to just block the return to iOS 11 and leave an open door for iOS 10.3.3.
Apple has probably stopped signing iOS 11 due to a serious battery problem in iOS 11 and has continued to sign iOS 10.3.3 . However, the battery issue applies to all iPhones. 70% of users upgrading their devices to iOS 11 are experiencing serious battery problems.
If you are an iPhone 6s user and want to return to iOS 10.3.3 , you can do the return process by using the following text before stopping Apple signing. Do not forget to take a backup before proceeding.
