nostr:npub1psdfxfpxz2cwmmnsk60y3nqpn2tqh9n24h4hstvfkwvr6eaek9js499sr7 

Haven’t read entire thread but I own and have used the following Markdown apps which are available for macOS and iOS

https://ulysses.app

https://www.mweb.im/index.html

https://ia.net/writer

I live in Ulysses for longform writing, and I know that some authors like Matt Gemmell use it for writing books (which he outputs to EPUB himself in the app). He compared Ulysses to Scrivener back in 2016:

https://mattgemmell.com/thoughts-on-ulysses-and-scrivener/

& his site has a few scattered posts since then on his workflow