Vivaldi ships with a load of preselected bookmarks. Mainly big news sites and some online stores. It seems like there is some affiliate marketing going on there. Some of these bookmarks link to a vivaldi.com page that redirects you to a siteplug.com page which again redirects you to the actual page.
Siteplug seems to be the service with they use to monetize the traffic. Notice that the redirect link doesn't offer a https version. Neither does their website [0] that also just shows me a dead bird on most pages [1].