Ask HN: How to transfer ownership of a software product?

After maintaining an app[0] for 7 years, I wanted to take it offline. I don't want to maintain now pay for it anymore. I announced that it would go offline in August 2021. A user got in touch with me and offered to take it over.

This wouldn't be a problem if it was just code and a domain, but this app hosts 22000 text notes from 6700 users. Some might contain sensitive information. I do not want to give that data to a stranger.

What would be the best course of action?

[0] http://markdownnotes.com