Place this app in nextcloud/custom_apps/
Install this app and configure it with OCC:
occ integration_jupyterhub:set-url <URL to Your JupyterHub>
Or under Administration -> Additional settings
Create an OAuth2 Client under Administration -> Security and note Client identifier and secret for use later.
You need to configure a bunch of stuff in Jupyter Hub. A full configuration guide can be found here: https://wiki.sunet.se/pages/viewpage.action?pageId=178290700