Suppose I use an artificial intelligence (AI) program to create a picture of a famous person (e.g. a politician or movie star), Suppose I then use the picture in an article or book in a manner that isn't defamatory and doesn't violate the person's publicity rights. Let's say it's a political cartoon that is insulting, but it falls within fair use.
If I use a commercial service (e.g. Shutterstock) to create the picture, then my understanding is they would own the copyright, whether I modify the picture or not.
Question: If I use a non-commercial service, would the picture be in the public domain? If so, I'm assuming I could claim copyright if I substantially modified it, right?