The hard part IMO is surviving the passage. The Cape Horn waterway is damned rough in the best of weather. Even today modern ships try to avoid the passage, preferring the Straits passage. Continued communications with SA will be difficult at best.
I prefer this one: Australian Aborigines develop the scientific method and modern technology ca. 20,000 BC but don't go on a mad imperialistic dash to conquer the world. Some of them set up scientific bases in Antarctica and these become permanent settlements, population ca. 1000.
Yeah, unlike Greenland, Antarctica has very poor diversity in land fauna and flora. Even the Inuit need wood from trees to create some of their tools, that are essential for everyday survival. And living off seals, penguins and sea birds all the time is really not the best of diets. Even the Arctic would offer a better one.