Archival sites could let you download cryptographically signed copies of the archived pages. If they get removed from the archival site, the authenticity of your local copies can still be attested.

Storage media and authenticity have zero overlap in the venn diagram. Authenticity is a cryptological feature of the internet, not a topological one.

The reason you believe that you're reading something on news.ycombinator.com right now is not the path by which the bytes were copied from one interface to the next before getting to you, but the certificate and signature that confirms you have a valid HTTPS connection.

True, it's next to useless as a proof of anything for wide audience...

But what does care about local storage in this brave new gaslit world is my own sanity, for one.