You can sync with notes in your cloud. I guess if you set it up in a cloud folder that is shared between users, then multiple people might be able to share notes. I did not try it though.

I am not familiar with Google Keep Notes, so I do not know how that one works.

Edit: wrote “calendar” instead of “notes” for some unknown reason

I can recommend SilentNotes, an actual European (and open source) simple note taking app.

https://www.martinstoeckli.ch/silentnotes/silentnotes.html