Hopefully you didn't notice, but there was a little hiccup this morning that resulted in a full-blown site migration to a new hosting instance.
I didn't closely RTFM. Although there is reference to in-place upgrades for Bitnami Ghost images, hidden more deeply on other pages are a big warning that basically says just start from scratch on a new instance and migrate ... it's safer.
Well, they were correct about that. When the in-place upgrade went pear shaped it left me with MySQL / NPM and God knows what other dependencies completely fubar'd. Even attempting to restore the full application-level backup of the stack resulted in further pooching.
So rather than spend the next 6 hours troubleshooting - I cut my losses and followed the 'deeply hidden' advice. I spun up a new hosting instance, imported the Ghost json export (which I thankfully also took and stored locally) with all the posts and most of the config (sans the custom images, which I did have backed up locally), and was able to get the site back up and running!
Things may still be a bit loosie goosie - I jumped forward about 30 minor revisions of Ghost, and there is probably stuff that I locked down or enabled originally that I've forgotten to do this time round.
Before you all say 'why didn't you just roll back to your last daily snapshot?' ... well that would have involved me having enabled daily snapshots in the first place now wouldn't it. Yes, they are now enabled.