Root cause analysis:
1. I (don't remember, but assume that I) started an upgrade, but got distracted
2. the newly built containers sat there not bothering anyone
3. I was messing around with Docker and caused 'em to replace the existing ones without realising
4. the database wasn't migrated so the new containers didn't work
5. everything was broken and I didn't know how to fix it, had analysis paralysis and eventually gave up
Sooooo not great.