DuckDuckGo is, indeed, listed in Safari History. I see it all the time when I use it. Sometimes, however, History does not show a site if I open it in a separate tab.

Jon

macOS 11.7.10, iMac Retina 5K 27-inch, late 2014, 3.5 GHz Intel Core i5, 1 TB fusion drive, 16 GB RAM, Epson SureColor P600, Photoshop CC, Lightroom CC, MS Office 365