There are things like Mymind (SaaS) or Karakeep (selfhosted) that do this, though they require you to explicitly save the pages instead of indexing everything by default

I haven't used this but looks someone created a self hosted version of Microsoft's Recall

https://github.com/openrecall/openrecall

I would really like to see integration between Karakeep and SearXNG so that I could combine online search engine results with my self-hosted bookmarks serice.