Thank you for replying. The next morning when I started up Opera again, Duck Duck Go was the default search engine. Not sure what happened, as I had tried many things -- relaunching in safe mode, switching to Google (Opera's default) and then back to Duck Duck Go, closing Opera and re-opening, etc.... but it's all working fine now.
Sorry, but how do you actually turn this on?
I installed Tampermonkey and copied the script in and the dashboard says it's enabled, but Tampermonkey says no scripts are running and a search on DuckDuckGo just searches on DuckDuckGo.
Google doesn't separate search results that much anymore - like they used to do for different language areas. Sure China still get's the treatment. If Opera continues to be the only browser with forced default engine ~ step 1 would add option to choose a country code (ccTLD) from a short list including .com!