Unfortunately, I didn't do a backup before attempting this upgrade and, naturally, I've brought down my nextcloud installation.
Ah well. Here we go...
@sconlan All avoidable things, of course. This is what happens when you don't have enough time to properly do the thing you are trying to do! :-D
I went through the effort of setting up full VPS backups... and then I only ran a single test and never finished actually automating that.
And, of course, I've never restored from a backup...
Woohoo! Successfully restored!
Unfortunately I am set back to late October... but still! :-D