Apple has now permanently stopped signing iOS 13.4, making it impossible to downgrade from a later version. With the closing of signatures, users who have updated their iPhone or iPad to iOS 13.4.1 can no longer downgrade and return to iOS 13.4.
The decision to discontinue the signatures of the various iOS has repercussions, especially on those who jailbreak their devices since a potential unlock of iOS 13.3.1 would now be useless for those who have already updated to iOS 13.4.
Recall that iOS 13.4.1 solves an issue where devices with iOS 13.4 and iPadOS 13.4 could not participate in FaceTime calls, together with iOS 9.3.6 devices and earlier versions, or OS X El Capitan 10.11.6 and earlier versions.
In addition to fixing the Settings app problem that prevented the selection of the Bluetooth choice from the quick actions menu on the Home screen.