I’ve been keeping the site up-to-date; I recall the postgres upgrade some time back and I handled that then. I don’t recall seeing anything about it this time around, but it’s easy enough to run another rebuild. But while doing that, I saw:
…and indeed import is running. So I stopped that, and once the rebuild finished, the site came back up.
And the Let’s Encrypt cert is renewed (it seems several were issued today, which is a little troublesome), so all’s back now. Thanks for the quick response.