Naturally, I didn't do regular backups. Most of the data I have from a 2019 backup, but there's a metadata database that I don't have a copy of, and will need to reconstruct from scratch. Thankfully for my case reconstructing will be possible - I know that's not the case for everyone.
Right now I'm feeling pretty stupid, but I only have myself to blame. For their part, OVH have been really good at keeping everyone updated (particularly the Founder and CEO, Octave Klaba).
I believe that when I signed up back in 2017, the Strasbourg location was advertised as one of the cheapest, so I can imagine a lot of people with a ~$4 / month OVH VPS are in the same situation, desperately scrambling to find a backup.
(For those that have a OVH VPS that's down right now, you can find what location it is in by logging onto the OVH control panel.)
[1] https://twitter.com/olesovhcom/status/1369598998441558016