They're making more than $100mm a year via ads and have been profitable since 2014 according to this Techcrunch article: https://techcrunch.com/2021/06/16/on-a-growth-tear-duckduckg...

They use Bing's ad network (or at least they used to) and don't expose any privacy details about their users, so advertisers can't target you based on demographic or psychographic information.

They run ads based on keywords, not the person doing the search. They also earn revenue as an affiliate. (You click an amazon link and make a purchase. They earn a small commish off of it) I've been using duck for awhile now.

Pretty sure their results are just forwards of Bing, so not sure the operation is as massive as you might be thinking. DDG still shows ads, they just don't use tracking.