Why is my “more block” missing?

I haven’t used it, but I just realized that I don’t have the /more block available on my site.

I’ve set up a cloned devsite with twenty twenty three and there’s no /more block there either. So it’s not in the theme (same behaviour both with tt3 and Neve), and even if I disable all plugins on the devsite, I still don’t have the block.

I guess it is deregistered somehow, but I have no idea how. Any idea where to look to find out? And what to look for?

The page I need help with: [log in to see the link]