Private NC instance and data sharing

Hello.
I was wondering how I could use NextCloud to setup some kind of exposed data based on a private NextCloud server.

Is there any NC apps that allow to sync part of the data with an external provider? Such a service would be great for both personal and professional use cases: having a private NC instance with part of the data accessible through an online platform .

Thanks

Through WebDAV it is possible to share data with a variety of 3rd party apps. I’d use that…

Alternatively, adding /preview after a publicly shared link shows the file (if it’s an image, not sure what it does with other files, maybe direct download).

Would there be any app that already do such a service ?

If I were to code my own NC app so that I can basically sync some NC folders that would be flagged as “MY-NC-app shared”, are there any tutorial for this specific features : flag folders on NC interface AND sync from a non web accessible NC server (or at least push from NC server to the remote host)