Just looked it up since I was sure I had read they had their own. On their wikipedia article it says:
In its early days on the Internet, the Qwant search engine relied on Bing to provide more relevant results. In 2016, Qwant claimed to be increasingly using its own results from its own exploration robots. It is still at the status of hybrid engine.[89] In 2020, Qwant claimed to have exceeded 50% of independent results for web searches, and 70% for all researchs
Just looked it up since I was sure I had read they had their own. On their wikipedia article it says:
so I guess it’s both bing and their own thing.
So, ddg and brave also have own indices. But i dont think, that it is matter, anyway they send data to 3rd party services.