Raymond Zeitler over at Ray on Emacs has a nice post on copying the link at point in EWW. It’s sort of hidden so that’s the reason for his post and this one. He decided to write his own because he couldn’t find anything that already did the job. It was only after he wrote it that he stumbled on the existing functionality.
The short answer is that the u key does just what he wanted. The longer answer is that sometimes w also works. The documentation says that w copies the URL of the current page but if the point is on a link, it will copy the link’s URL instead.
I’m finding that I’m using EWW more and more so I’m glad to have this information. Zeitler has more details so be sure to take a look at his post.