Hello.
I just found the Joplin project here on GitHub.
It is a note taking and task management solution with clients for Windows, maxOS, Linux, iOS, and Android.
Syncronisation can be done in various ways (OneDrive or file right now only) and Nextcloud syncronisation is one of their priorities. However it seems to be blocked in the moment by a ReactNative bug. See syncronisation in the README.
So this is more a heads up for something that hopefully comes soon.
Btw, I have no relation to the Joplin project and just thought I share this here.