Notes - easy access

Before I opened an account with mailbox, I used Disroot. I liked that they used Nextcloud for both the cloud drive but also for notes. A simple open source app that:

* gave me direct access to my txt files (which are my notes)
* supported markdown (a nice to have)
* allowed me to access the notes, even if offline, because there was a local copy that synchronized with the server when changes happened.

As far as I know, there is no similar setup with mailbox. Ok I can access the drive using OX (which is not open source - have no idea why mailbox even uses this), but the notes (txt files) are more "buried" than I would like.
Oh and sort of a side note, when I moved from one provider to the other, I realized that mailboxes has this "Office" integrated in their suit. It works terribly on mobile. At first I was converting my txt files to docx (again, why use MS's format) because I thought that was how I would be doing things moving forward. Right now, I'm going back to txts