How to insert content in database after user is created

Is it possible to insert content to the database of an app everytime a user is created?
For example I got the notes app from the nextcloud tutorial and want to add a welcome note for every new user.
I am using nextcloud 14 and I would like to know if this is possible and how to do it.

As usual it is worse the read the administrator documentation to find an answer on how to Providing default files or to ask aunt G. for help.
Here you will find an article in German language, covering this point:

The problem is not about providing default files. That’s an easy thing to google.
I was wondering if it is possible to provide default data for any other app, not just files and directories.