I use:<p><a href="https://infinitysearch.co" rel="nofollow">https://infinitysearch.co</a><p>It's Private and it's open-source!
also, it's a search engine
(not meta-search-engine, even if they retrieve results from others they have their own crawler and index)
I'm not sure if it's necessarily private, but YaCy has been awesome. It's a decentralized search engine that has surprisingly good results in my experience.<p><a href="https://yacy.net/" rel="nofollow">https://yacy.net/</a>