1) downloaded & installed XCode 10 GM Seed
2) developed in XCode v10 beta, app requires iOS 12 (ARkit)
3) XCode Archive Validation fails
http://www.davidkellerinteriors.com/AppleSupport/ValidateFailure.png
4) Upload fails for the same reason
5) seems like someone failed to flip the switch to allow iOS 12 apps to be accepted, or I have made a mistake somewhere (quite possible)