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...
If I remember rightly, the backend update takes a long time as the database needs to do a particularly slow schema update. https://old.lemmy.sdf.org seems to still be ok.