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Federated Search Engine?
(beehaw.org)
If it's free and open source and it's also software, it can be discussed here. Subcommunity of Technology.
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SearXNG is probably the closest equivalent, as it's decentralized, you can host your own, and you can grab search results from over 100 engines with it. Search engines don't really federate like the Fediverse does; they just query each other as proxies for you and return the search results.