LPT: You can also set the search engine of private windows to noai.DuckDuckGo.com if you turned off AI summaries on normal windows.
If you, like me, use DuckDuckGo as a search engine but are annoyed your preference for no AI summaries couldnt carry over to private tabs. I much more prefer a Wikipedia snippet or the like.
Hopefully, this doesn't get nerfed. 🙇🏼♂️
You can tweak all the options however you want without being signed in, and they have a box on the right for the customized URL for those specific settings. Save as a bookmark or set as the search engine. Done.