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?