Can vouch for Hister! In the fairly short time I've been using it, I already had a few sites disappearing or changing content and hister kept the juicy information accessible.

It was painless to set up and quick to use when needed, too.

I also use Singlefile and Obsidian Web Clipper a lot, but Hister has been great and is now a first-class citizen in my system. It helps it works passively for those things that don't look important when you read them, but become relevant later.

By default it only keeps the latest copy of sites so I'm not sure how that prevents replacing with 404?

When it gets a 404 it doesn’t overwrite the existing copy

What if you get a 200 but just a "This is not available any more"?

I am using both Linkding and Linkwarden self-hosted and archiving my bookmarks as HTML, PDF, and screenshot (I might be overdoing it) without the need for any additional dependency like client software or extension. Linkwarden works better at archiving things like Reddit, but now with the anti-scraping mechanisms in place it might het harder to do anyway.

I realized I really need this when one website which was a treasure trove for PowerMac technical information and assembly guides just went dark. Some of that info I could never find elsewhere. Linkrot sucks if you're in the middle of an (admittedly drawn out) personal project and your source of information vanishes with no trace. Belt and suspenders from now on. Might give Hister a try.

I just started using it, and to my surprise it only saves the sanitized html content, no scripts no css. I'm thinking of pairing this with archivebox. But hister is amazing. I love it. It's from the creator of searxng if I'm not mistaken which is another piece of great software.