I just did some tests on DDG (sorry OP, not related to SearXNG). If you use it normally, they put a lot of images from URL like improving.duckduckgo.com/t/we?monitor=you&spying=secretly&id=etc (supposedly for improving DDG by gathering statistical blah blah). Their no-JavaScript version is much less invasive.
Solution(s): 1) uBlock is highly recommended, 2) if possible disable JS, 3) try Tor Browser, which is just an anonymity version of Firefox