You got me interested and I've tried it now. I've tried sharing a document and it just gave me a sharable link - doesn't sound too hard (it's not revocable because the URL contains a key, I guess, but that's a technical problem, not something non-technical person has to do)

That's the approach I used, but I wanted a document I could collaborate on and without having the risk of leaking it on the internet. In GDrive it's as simple as share -> specify email address.

In cryptpad you have to share your profile, the person has to "add you to their contacts" from your profile page, then they will appean in your contacts and you can add them as collaborators. The reverse is also an option: ask them to share their profile link, then you can add them. Unfortunately non-tech person don't even understand where their profile link is.

There is also a concept of "team drive", which is cool, a bit rough around the edges. In that case you can send invites to people and they can join and share a single directory, which is great.

Overall nice piece of software I'd say!