On my PC I use nvim with a directoiry and .md files. I sync that one via my nextcloud instance, so I was looking for an app that could do exactly that, read and edit my nextcloud directory with my markdown files.
Only one app could do that: Quillpad. But the sync feature doesn't work right for me, so I went a more extreme way: I just open termux und edit with nvim. Like on my pc. Same plugins and all. I sync those notes from my phone via syncthing then.