Hi,
I've currently updated my server system to ElCapitan and the actual version of OSX Server and Xcode. The Server is up and running and I can get to the point of selecting the target, but apparently there is no iOS platform on the Server. It says:
"This server cannot build for any of the platforms supported by this scheme. Available server platforms: OS X, watchOS."
However xcode there is runningn and I have simulators installed for iOS 9.0 and 8.4