After testing these four apps, Simplenote is the one that stuck. It does exactly what I needed: quick notes with Markdown ...

Joplin is a free open-source note-taking and task management app that gives you markdown notes, notebooks, tags, and plugins ...

You probably use the Notes app all the time on your iPhone. It’s the simplest way to quickly jot thoughts down when they come to you. It’s simple enough, in fact, that many of us use its surface-level ...