I've recently had Apple Notes mess up my notes: I can still extract them from the notes.db file with a binary editor to an extent, but it's not a valid sqlite file anymore. I am not even sure what happened (did my laptop run out of battery or something else, I don't know).
I didn't have them synced to the Apple Cloud either as it's a corporate laptop, but I advise against using them for what you want to keep.
I didn't have them synced to the Apple Cloud either as it's a corporate laptop, but I advise against using them for what you want to keep.