Ironically, the answer is buried 2/3 down.

  And here’s the trick to using it without having to click the ‘Web’ option buried in a menu every single time. Google does not make it easy, but by adding a URL parameter to your search—in this case, “udm=14”—you can get directly to the Web results in a search.

At the end the author shows how to configure Vivaldi to do this automatically.