Update on Migraciones from today: they're assigning appointments, but when you go to Migraciones (this was Av. Antartida) with a confirmed appointment, most people are rebuffed at the turnstile and told to wait for an email rescheduling their appointment. You're given no confirmation that your appointment was rejected, so if you need something, e.g. for your work, you're out of luck. The recommendation given was to continue extending the precaria visa (this should be assigned when you upload your documentation to the Migraciones website) until a rescheduled appointment comes through.
Why the email rescheduling the appointment couldn't be sent before the appointment date, to avoid people pointlessly going to Migraciones, is beyond my understanding, Migraciones is behaving in an even more imbecilic fashion than usual. There are 10s of people milling about in front of the DNM offices not knowing what to do next.