Can I ask how you managed to get this to work in the simulator in the first place? I'm simply trying to capture data and save it to a group container, but I can seemed to even print anything to the console from within the beginRequest:with: method. I'm assuming your code is within the SafariWebExtensionHandler class adhering to the NSExtensionRequestHandling protocol?

I believe the issue here is that the background scripts in iOS are non-persistent, so they aren't continuously available to view under the Develop -> Web Extension Background Pages menu, as they appear for macOS extensions. It is possible to debug the background script if an action is performed whilst the extension is currently active, by inspecting the _generated_background_page.html under the Develop -> Simulator menu item. However it gets frustrating if you need to debug your extension earlier on in the extension lifecycle. I'm not sure there currently is a way to do this. Hope that helps a little though.