Yandex is a pretty good search engine. Yandex is essentially what people think DuckDuckGo is, on the other hand DuckDuckGo is essentially is just Bing.
My understanding of Yandex was that it's just another user-information-is-primary-income search provider this time HQ'd in Russia, neither of which exactly appealing to the typical DDG crowd.
Though I'd throw Kagi out to anyone who puts a lot of weight on such things as being a more pure example than either.
Do you have a source for this? I'd be interested in reading the technicals of merging search results from multiple sources.
A Russian company having my data given the current state of relations between it and my government is less worrisome than Google having the same.
That said, this has nothing to do with ads. It's a matter of foreign intelligence.