One of the apps that ship with Nextcloud is Notes. It is not much more than its name says. You can open a note, type some text, and do some basic formatting stuff in markdown syntax. If you want, you can give each note a tag, which results in a folder, where that note is placed in. Those notes are synced as normal *.txt files to your file system in a folder named Notes, including the tagging subfolders. It's dead simple, but useful, as I described in my blog entry about writing a shopping list with org mode.

Twice a week I compile a shopping list, mostly for our local supermarket, but also for some smaller stores. Getting the finished list the easiest way to my phone was a thing that I wanted to automate for a long time.