I'm sure Joplin is excellent and I hate to argue one against the other. The markdown files in themselves should be independent. I have used several full featured, rather excellent, note-taking software, where the export is not "open". Obsidian is the only reasonable system I have seen where the software is up to date and it doesn't do anything with the markdown files to lock them in. I speak of this as a single user experience. And no, I don't like the idea of Mac Notes and Windows OneNote either. I'm all for note-taking apps which keeps the data/files independent.