Xcode 9 - no iOS 11 simulator
I seem to be pretty stupid, wasting too much time than necessary.
The new iOS 11 simulators were already included in the new Xcode, (however the won't appear in the settings of Xcode) . You can just open up the simulator (/Applications/Xcode.app/Contents/Developer/Applications/Simulator.app) and choose an iOS 11 device in the Hardware > Device menu bar.
Xcode.app can be Xcode-beta.app too.
In Xcode Version 9.0 beta 5 (9M202q)
In the menu Window > Devices and Simlators
- Click on the + button at the bottom left corner
- Choose 'Device Type': 'iPhone SE'
- Then 'OS Version': 'iOS 11.0' can be choosen
Have fun!