> If a search engine were to penalize ads, I bet a lot of those old sites would surface.
Maybe using an ad blocker to build a list of "websites that serve ads" (in addition to domains those ads are served from), and using that list to filter out results from an existing search engine API (like Duck Duck Go) would get you part of the way. But you'd probably need to search really far before you start finding sites that don't serve ads.
Kagi partially does that. I lt shows how many trackers a result has on its results page and lets you boost or downgrade domains in your search results.
Maybe using an ad blocker to build a list of "websites that serve ads" (in addition to domains those ads are served from), and using that list to filter out results from an existing search engine API (like Duck Duck Go) would get you part of the way. But you'd probably need to search really far before you start finding sites that don't serve ads.