There was a fanfic, Domination Centuries, co-written by Stirling himself, that showed the outcome of Ingolfsson winning.
Basically, the Domination pushed a bunch of orbital battlestations (that could enter the atmosphere as well) through the portal, made their presence known and stated their intentions....then arranged a time and place for the Earth's militaries to take their best shot (without risk of collateral damage, and with the Draka promising no retaliation).
Seeing evidence that megaton-yield nukes weren't effective weapons, the nations largely surrendered peacefully, and the resistance was limited to wildcat guerillas and some groups sponsored by the Samothracians (implied to be Lafarge, offscreen). The Draka cut a deal with the Samothracians (who shut down their sponsored guerillas), and eliminate the wildcats (hard to have an active resistance when the cops have real truth serums and can download your memories).
A few decades later, the Earth is a well-run Draka colony (though the human serfs mostly belong to the State at large, rather than private owners, and have rights....and the Draka decide not to turn the population into homo servus, due to evidence that servus & drakensis are less imaginative than baseline homo sapiens). Most regular folks don't encounter Draka in their daily lives, as they are a thin layer (low thousands) on top of a massive (low billions) human population.
The primary author of the fanfic (Sterling, IIRC, wrote a few sections from Ingolfsson's POV, and shared some general insights) has a serious thing for the D & S side of the Draka, so the fanfic is basically the Draka being awesome and sexy, and awesomely sexily killing or seducing those who oppose them. YMMV.