Flutter: iOS Emulator for Windows
If the purpose is only testing how the UI works on iOS, then Flutter Inspector will do the job.
Click on the Flutter Inspector from the right pane and click on 'Toggle Platform Mode' from the top menu of the newly opened box. This will change the UI of the running app on your device.
Most iOS developers use (in a separate window) VMWare WorkStation (a virtual Machine) and install MacOS with XCode.
You can always go back to VMWare, but these 2 links might be helpful.
https://www.dreamytricks.net/ios-emulator-windows-run-ios-apps/
https://developer.xamarin.com/guides/cross-platform/windows/ios-simulator/
It seems there is no direct way to run the app on iOS emulator unless you use Mac pc or laptop. However, this article provides you with an indirect way to run the app. Developing and debugging Flutter apps for iOS without a Mac