Having read DuckDuckGo's privacy statements, you might decide to switch Safari's default search to DuckDuckGo. If we enter a new search in Safari, we can then search the logged data to see who the search terms are actually sent to.It would be interesting to see what breaks if you put network Access Control Lists to block access to *.apple.com. I'd think that it might effectively brick your laptop.
The logs show that a copy of your Safari searches are still sent to Apple, even when selecting DuckDuckGo as your search provider, and 'Spotlight Suggestions' are disabled in System Preferences > Spotlight.
No mention at the article as to what (if anything) Apple does to fight National Security Letter snooping. My guess is little or nothing.
Remember, Linux is free.