If that’s not a Google clone I don’t know what is.
They're looking at how users use Google Search because the data's there. They're making a competitor to Google Search. That doesn't mean they're rebuilding Google Search's SERPs, or making a Google Search “clone”; I've got results from Cliqz for queries I'm confident have never been put into Google before, meaning it's functioning as an independent search engine.
This. Having worked in past life for one of their competitors, can confirm - what users click on (in SERP) is one of the most powerful signals for ranking. And who got (almost) all the clicks in the world? Google!
That's why it's so damn hard to beat them. It's the unreasonable effectiveness of data: more data (which they have almost all of) usually beats a smarter algorithm, and with 20 years R&D, theirs is surely not dumb.
Do the clicks belong to users or Google, that's an interesting question, though.
So there are Google and Bing - any others?
Qwant is a France-based search engine that has a similar privacy focus to DuckDuckGo.
Million Short tries to find sites that other search engines miss.
Wikipedia has a more comprehensive list:
In 2013 they said they were temporarily using Bing results they purchased as "training data" [wikipedia].
They haven't given any updates on that I could find (in English, at least), but they recently proudly announced they have 20B pages in their index in an article on their partnerships with Microsoft [betterweb]. Google's index is 1500 times larger, so I'm not sure how competitive their own index is [goog]. And, if they no longer needed to rely on Bing results, wouldn't they announce that?
[wiki]: https://en.m.wikipedia.org/wiki/Qwant
[betterweb]: https://betterweb.qwant.com/how-microsoft-tools-strengthen-q...
[goog]: https://venturebeat.com/2013/03/01/how-google-searches-30-tr...