Xcode 9 iOS Simulator becoming black screen after installing Xcode 10 beta

try workaround, delete Library/Developer folder and start it again

Try running defaults write com.apple.CoreSimulator.IndigoFramebufferServices FramebufferRendererHint 3 in Terminal (source). Note that this will force Simulator to use OpenGL instead of Metal, so you'll want to re-run it with 0 once this gets fixed.