I used to use Joplin, I liked that it integrated with my Nextcloud, and the markdown format. However, the way that it handles the markdown files was too black-boxey to me, with the way it split them up in a weird scheme.

Now I use Ghostwriter with straight markdown files inside my Nextcloud folder. So I still get the syncing functionality, but a more flexible setup that doesn’t require a specific app to access all of my notes.