I am trying to add a new screenshot in either the png or jpg format to a product page of an existing app. When I try to reorder the screenshots, App Store Connect says the new screenshot is not in the RGB color space. Preview, which created them, and Finder both say they are in the RGB color space. What should I do?

In the past QLThumbnailImageCreate would return an NSImage from a url pointing to a webarchive. It's not doing so now. Is this a bug, or do I not understand something?

There are a number of answers to this question on the web. The latest that I have found is for early 2020, and it no longer seems appropriate. What is the current method?