Here are the guidelines (as of this writing) for uploading app screenshots for App Store as per Apple document, Submitting iOS Apps to the App Store:
Upload screenshots to App Store Connect. Upload screenshots for the new iPhone XS Max or the 12.9-inch iPad Pro (3rd generation). Screenshots will be automatically resized for iPhone X and later, or for the 11-inch iPad Pro. Starting March 27, 2019, all app submissions for iPhone or iPad, including universal apps, will require screenshots for iPhone XS Max or the 12.9-inch iPad Pro (3rd generation).
Upload screenshots as they are, with no modifications. The rounded corners will be automatically applied after upload.
If you add text descriptions to your screenshots, keep text away from the corners to avoid cropping.
Leave the home indicator in the screenshot, if it’s visible.
There are no specific instructions about items shown in the status bar. You can leave whatever icons are visible as is. Also, some apps may choose to hide the status bar, so naturally it won't be visible in the screenshots.
There are no specific instructions on value and format of the time displayed (and whether or not it should be displayed) in the status bar.