This video gives a workaround for the following error:
An unknown server-side error occurred while processing the command. Original error: Xcode version 9.0 is not yet supported
Xcode version 9.0 is not yet supported error
https://www.youtube.com/watch?v=mGpfjbPsO20
You can inspect elements with Xcode 9 + iOS 11 + Appium version 1.5.3 (Ara)