Good luck. We definitely need more search engines. (That Google announced to lower the PageRank(R)/site score for non-HTTPS sites is a clear indicator that they about to cross the line (monopoly). And no, DDG and most others are "just" meta search engines that rely on Yahoo Boss ($$$) which future is uncertain and relies on Bing.)

There was "Wikia Search" by Wikipedia founder Jimmy Wales:

"Wikia Search was a short-lived free and open-source Web search engine launched by Wikia, a for-profit wiki-hosting company founded in late 2004 by Jimmy Wales and Angela Beesley.

Wikia Search followed other experiments by Wikia into search engine technology and officially launched as a "public alpha" on January 7, 2008. The roll-out version of the search interface was widely criticized by reviewers in mainstream media. After failing to attract an audience, the site closed by 2009."

https://en.wikipedia.org/wiki/Wikia_Search

I used Wikia Search back then, it was good enough (like Bing in comparison to Google back then).

It was based on Apache Nutch and Solr/(Hadoop(?)/Lucene ...

Maybe you can rely on Lucene or SphinxSearch projects to kick-start.