After the release of iOS 12.2 for the past few days, Apple has officially stopped the signing of iOS 12.1.4
In short, a few days after the release of a new version, Apple interrupts the signatures of the previous release, thus making it impossible to downgrade from iOS 12.2 for all devices.
At this, unless there are some serious bugs, it is difficult to downgrade your product unless it involves the less common and supported jailbreak practice.
The fact that Apple stopped to signing also makes it impossible to restore iOS 12.1.4 via iTunes, which will then force you to install the latest version, otherwise, you will be unable to activate your device.
Given the support for second-generation AirPods, we suggest upgrading to the latest version 12.2 of iOS in order to introduce other small features added by Apple with this new version.