So I exported all my Nimbus notes on Mac as html and then wondered what I could do with them apart from re-import them back into Nimbus (the .zip drectly imports). They definitely do not import successfully to nearly all other apps of a similar nature except..Apple Notes I discovered.

It does a really good job of rendering Nimbus notes! The only caveat is you have to decompress the zip and import the resulting folder. But take a look: first is Apple, second is Nimbus, not bad. The Nimbus table was even rendered, not completely successfully but OK.

Obviously the Nimbus is more beautiful but as an emegency backup should Nimbus ever disappear I think I feel secure I have a working back up.

Lots of work involved but there you go.

And I guess this might open up communication with other apps by exporting out of Apple Notes, which is going to have more compatibility I imagine.