If you downloaded the Xcode xip file instead of getting the app through the macOS App Store, you also had to decompress the more the 10 GB file in order to get the .app file. You might also have tried to decompress the file using the default app called “Archive Utility”. Not only does this app take a substantial amount of time (hours) to decompress the .xip file, but to your surprise the decompressed Xcode app shows you the error message “Required content for iOS Simulator is missing” or “Required content for tvOS Simulator is missing” once you try to open it. The error is actually due to the way that the xip file has been decompressed. So what’s the solution? Instead of using the “Archive Utility”, simply put the xip file into the Applications folder and use the command line xip utility instead:
# cd /Applications
#xip –expand Xcode_X.X.X.xip
xip: signing certificate was “Software Update” (validation not attempted)
xip: expanded items from “/Applications/ Xcode_X.X.X.xip”
The xip command line utility not only takes much less time than the Archive Utility to decompress the files, but the error message no longer shows up once you run the Xcode app.