What is a custom captcha for WordPress (content/entire site blocking by captcha)?

Question

CAPTCHA

The task is the following - when a person enters a certain article, he must enter a captcha to get to it.
It can also be implemented through blocking the entire site - the first time you enter, it asks for a captcha / enter a password.
It would seem a simple task, but I could not find a plugin for implementation. I would be glad if you advise plugins or other ways to implement such a simple scenario)
From what I tried: mostly content blockers work through a password and only on the "part of the content" that you take into tags. That is - a person sees the entire site, the title of the article, but not its content. And that doesn't fit very well.