downgrade from ios 11

iOS suggs in so many ways, not only by turning iOS and the app store into a kindergarten, but above all by emptying my iPhone 6s+ battery within 6 hours or less. So I need to downgrade to iOS 10 – like many, many others.

There are a lot of threads concerning this need, however Apple seems to have locked us in: All iOS versions previous to 11.x are not signed any more.

So my questions is: Which procedure works still? (as of november 18, 2017)

Thanks a lot!