BuddyPress.org

Thanks @vapvarun, I tried that before and it almost broke my site. I stopped the process and went back to my main theme. By then I had lost all of my Composer settings, so I’d rather not try that again.

The only thing I found that helps temporarily, is switching off Jetpack. Then at least the avatars in the footer widgets (such as who’s online) come back, but the avatars don’t reappear on the member pages. And as soon as I refresh a page, the footer widget avatars are gone again.