After successful Mac upgrade, Xcode 27 works but my Xcode 26.5 and also Xcode 26.6RC show a no entry overlay on the icon and a launch alert saying not supported. I did get it to launch by opening the App Package Contents and opening the Xcode inside the MacOS Folder. So you theoretically can submit to the App Store from MacOS 27.0 The behavior of the icon needs fixing. Yes they were both the Apple Silicon Xcode downloads.