As far as I know, it's almost impossible for any significant number of people to live on land that remains covered with thick ice for the entire year around. Even northern Siberia, Canada, and Alaska are mainly tundra rather than ice. The parts of Greenland that are inhabited are mainly southern coastal areas - the only places that aren't ice-covered. I think that the only large piece of land in Antarctica that isn't permanently ice-covered is the peninsula that curves out northward toward the southern end of South America. I think the climate there is tundra-like and roughly equivalent to the northernmost parts of the Eurasian and North American continents. I doubt it could hold millions of people, though. Maybe tens or hundreds of thousands at most. None of the other tundra areas on earth hold millions of people.