It has native clients for Linux, Android, and all files are plain MD.
I can freely sync everything with third party apps. Total freedom.
As a side-effect, I just noticed that I prefer a long markdown file with proper headings (and an outline on the side) than Milanote's board view, which initially felt like a more free form better suited for unorganized thoughts and ideas for writing that I had (I use it for my fiction writing).
I still can have documents as a list of loose thoughts, but once I am ready to organize my ideas, I just use well written and organized headers, edit the content and now I have a really useful view of my idea.
Honestly that's more you subjectively than database v files.
On the other hand, you get to implement concurrent access yourself. Multiple apps working on the same files simultaneously only works when none of them makes a mistake with caching or locking.
https://xenodium.com/an-ios-journaling-app-powered-by-org-pl...