[PLUG-TALK] Can't get rid of DuckDuckGo

[John Jason Jordan]

Suddenly today every time I search now DuckDuckGo gives me constant
ads. Furthermore somehow they have managed to make DuckDuckGo immune to
the ministrations of the ad blockers I have installed in Chromium.
Moreover, I decided to switch to a different search engine, and I
discovered a new one in the drop-down list - Ecosia. I selected it, but
when I try to search I still get DuckDuckGo. Ecosia is still selected
in Chromium settings, and I even restarted Chromium, but DuckDuckGo
won't turn loose of the browser. 

How can I get rid of DuckDuckGo?