For the PreviewProvider, is it possible to set the ios version which the preview will be made for or the preview will always use the latest ios version (e.g. ios 17)?
Is it possible to make a swiftUI preview for a specified iOS version
You cannot specify the OS version on the preview directly, but you should be able to setup a simulator for the older OS and pick that simulator in the canvas as the destination of your preview.
image here
You will need to create a new simulator for the other OS version you want if you do not already have on created. You can do this in the Simulators tab of the Devices and Simulators window that is accessible from the Window menu in Xcode (incidentally, you would do this same thing to create a simulator for build and run that was an older OS version). Once you have created your new simulator it should be available as a destination for your preview.