If you want to check whether an article ever appeared (even if it's no longer there), then something like https://en.wikipedia.org/wiki/Certificate_Transparency would be enough.

No that's not a blockchain, at least not for a useful definition of blockchain (see https://www.schneier.com/essays/archives/2019/02/theres_no_g...).

One interesting thing I have been seeing recently is newspapers quickly changing news a few hours after they posted it, in reaction to public opinion of said news (or maybe some editorial "request").

In th BBC its quite egregious, they have been posting some news, and a few hours later changing the headline and the photo, to either something meaner and an uglier photo of the same person, or the opposite, a much more neutral/flaterring headline and a PR photo of the person.

If those changes were on the blockchain, UK citizens could demand their money back for what they pay for the BBC as it is a ridiculous practice that should not be paid by taxes. But again, I doubt the Italian newspapers saves their own slanted coverage for their own users to see.

I think some of the most noticeable ones tend to be on big political news. It happened fairly quickly with Truss. All "happy" headlines and smiling photos, to ugly photos and total lack of positive adjectives as the news of her departure became more obvious.

Sometimes they have done it on the same piece of content, a few hours apart as the narrative changed. The content of the piece was untouched but the photo and headline on the front page tell the opposite story all of a sudden.