I have just noticed that the topic was split.
I'm currently updating the GSoC application. In the course of this, I would like to publish the first project idea.
Porting the web-app or have a Nextcloud app created would be the idea.
Now we have this here 
In general, it is needed
- storage
- back-end server (what may run within another application)
- front-end apps
Regarding Nextcloud
- is it smart to run the back-end as an app in Nextcloud
- shall it be installed on the same server (as e.g. docker image)
- an app is written what communicates via the API
- port (fork) the web-app, to make it run as nextcloud app
Currently, I don't know how to describe the project(s) 
.
Whatever going to happen, it should be done in such a way that Joplin is not limited to be used with Nextcloud only, when you want to integrate it into another collaboration app.
Of course, Nextcloud would be the pilot and thus the one with the most drive most likely.
description should be as described in