Xcode 10.3 (10G8) (App Store)
Mojave 10.14.5 (18F132)
Problem: No Simulators appear in the active Scheme popup menu.
The Simulators were available and working in Xcode 10.2.1
The Download Simulators window informs me that iOS 10.3.1 is the current Simulator and that the latest iOS Simulator available for download is iOS 12.2.
If I attempt to perform Add Additional Simulator (e.g. iPhone XR), I get the error:
Invalid runtime: com.apple.CoreSimulator.SimRuntime.iOS-12-4
I have reinstalled Xcode 10.2.1 alongside Xcode 10.3.
When using the newly reinstalled Xcode 10.2.1. the Simulators are are available, and the chosen Simulator (iPhone XR - 12.2) works.
$ xcrun simctl list runtimes
== Runtimes ==
iOS 9.3 (9.3 - 13E233) - com.apple.CoreSimulator.SimRuntime.iOS-9-3
iOS 10.3 (10.3.1 - 14E8301) - com.apple.CoreSimulator.SimRuntime.iOS-10-3
iOS 12.4 (12.4 - 16G73) - com.apple.CoreSimulator.SimRuntime.iOS-12-4
tvOS 12.4 (12.4 - 16M567) - com.apple.CoreSimulator.SimRuntime.tvOS-12-4
watchOS 5.3 (5.3 - 16U567) - com.apple.CoreSimulator.SimRuntime.watchOS-5-3
Any suggestions are appreciated.