https://wccftech.com/downgrade-ios-12-gm-to-ios-11/

Here’s a complete step by step guide on how to downgrade iOS 12 GM back to iOS 11 (iOS 11.4.1) right away on your iPhone, iPad or iPod touch.

We all know the routine: you downloaded iOS 12 GM out of sheer excitement and Apple’s latest creation didn’t turn out what you expected it to be. We hear you. A lot of users feel that way at this point. That’s why in today’s guide we’ll show you how you can downgrade iOS 12 GM back to iOS 11.4.1 in a few easy steps.