Count me as another person with the same problem. iPad 10.5” with the smart keyboard. Worked fine with iOS10, but starting with 11 (11.0.1 was the first I tried) it periodically disconnects. The only solution I’ve found is to reboot, which has always worked without disconnecting the keyboard or anything else. Have had the problem on 11.0.1, 11.0.2, and 11.0.3.
I read someone else who said that turning airplane mode on then off fixes it, so will try that next time. But this is a pretty pathetic problem for one of Apple’s supposedly premier products.
Bruce