Xcode 16.1 beta2 的更新日志有一段说明：
The simulator runtimes are currently available on the Apple Developer website, but will no longer be posted through the website in future updates. Please use xcodebuild -downloadPlatform -exportPath command to download the runtime and then xcodebuild -importPlatform <path/simruntime.dmg> to install it. For more details, see Installing and managing Simulator runtimes. (133776444)
以后不在网站上提供 Simulator Runtime 的下载链接了，需要使用 xcodebuild 来下载：
$ xcodebuild -downloadPlatform iOS -exportPath 'Simulator Runtime'
$ xcodebuild -downloadPlatform tvOS -exportPath 'Simulator Runtime'
$ xcodebuild -downloadPlatform watchOS -exportPath 'Simulator Runtime'
$ xcodebuild -downloadPlatform visionOS -exportPath 'Simulator Runtime'
因为 Simulator Runtime 同时也包含了对应平台的 SDK，所以基本上是需要全部下载回来的。
安装 Simulator Runtime：
Xcode 16 开始，使用 xcodebuild：
$ xcodebuild -importPlatform "~/Downloads/iOS Simulator Runtime.dmg"
Xcode 16.1 beta 3 开始支持 -buildVersion 指定下载特定系统版本的 Runtime：
$ xcodebuild -downloadPlatform iOS -buildVersion 16.0 -exportPath ./SimRuntimeImages/
$ xcodebuild -downloadPlatform iOS -buildVersion 20A360 -exportPath ./SimRuntimeImages/
如果是 Xcode 15 以及之前的版本，使用 xcrun：
$ xcrun simctl runtime add "~/Downloads/iOS Simulator Runtime.dmg"
