A recent update of WordPress has broken a few things around here. Noticed so far: the Classic Editor can no longer save or preview (error 406); and the sidebar does not show up in single-article display.
(later) And the comment form is gone. Argh. Time to look for a theme that I don’t hate, until I get around to learning how to make one properly.
Hard to find a theme that does not look like a catalog or a travel magazine.