Federation is broken.
It's been broken for days - and that's not to say for months, because I charitably include the few hours it worked again lately for some reason.
I don't know if other instances are that thoroughly broken, because the rest of Lemmy seems to be chugging along just fine. It's just us poor SDF user suckers.
And no-one gives a rat's ass.
Truly pathetic...
I got a reply from membership@sdf.org:
I think it's working now.
At the bottom of the web UI it says: BE: 0.19.2
So I guess the upgrade is complete?
Looks like it. Everything seems to be working correctly for me now.