Correction: Yarns Microsub Server doesn’t implement Micropub. But wonderfully, it doesn’t have to since that can be handled entirely within the Microsub client.

As for @mikbl’s original question, I rarely (almost never) post images, but I do use Micropub to my site with automatic syndication to Twitter. I typically write a post in either alltogethernow.io or Indigenous for iOS, both of which allow me to set Twitter via Bridgy as a syndication target.

My site uses a modified (by child theme) version of SemPress.  I never got around to publishing my child theme, but it might be useful to so I’ve added that to my todo list