This is a replacement from "Auto Featured Image (Auto Post Thumbnail)".
Anyway, I think it's good that it is simple without any extra functions. I don't want this kind of plugin to be highly functional. Rather, I emphasize stable operation.
Originally I reviewed this in Nov 2020 at 5 stars. Sadly on WP 5.9.3 it seems to be half broken. When you run the tool it just says "Posts not found".
I had mixed results removing a an existing outdated featured image and when the post reloads in the Dashboard, the plugin did actually add the correct default image.
Unfortunately wasn't able to get a reply in the support section. Such a shame, I've found nothing as good as this was for this simple job. Hopefully normal good service and reliability will resume!
Having looked for a simple plugin to generate a featured image from existing posts, this did the job fast and efficiently. Only about 80 posts, it took about a minute. They all look great in the Divi Theme front end, which is set to display a full width blog post title. Saved a lot of time, no fuss, no bloat and you get the bonus of seeing tiny thumbnails next to the posts in the Admin Dashboard. It didn't lose the existing featured images I'd already set up manually.
Nice job, thank you!