DDG's statement on their sources is that they have over 400: https://help.duckduckgo.com/results/sources/?redir=1

But that is largely with respect to "answers" type responses, which they are not lifting from Bing. Search results come from partners "including" Oath/Yahoo and Bing. And I think Yahoo uses Bing. But I know that DDG uses Yandex sometimes as well, so there's probably a handful of potential sources they draw from for search.