I have met many people from South Africa and they are atheists (usually militant) plus our good friend Richard Dawkins is from South Africa.
Im not sure, I have several SA frriends and they are all devout Christians. All of the ones I know are Dutch Reformed with like 2 Catholics. Im sure it is there like it is anywhere, there are going to be atheists
According to wikipedia, which probably isn’t the best source as much as it is the most convenient, no. 79.7 percent of the population is Christian.
Most of the Afrikaaners are Dutch Reformed/Calvinists of some kind, and quite strict about it when they are practicing their faith. Of course, the world as it is means that most Afrikaans people today under 30 couldn’t care less, though in many areas they still hold true to the Calvinist ideals and they are somewhat God fearing.
Most English South Africans are mostly Methodist/Evangelical/non-denom if they are Christian. Again, though, most under the age of 30 are either agnostic or outright atheist. In my circle of (~15) friends only about 2 identified as Christian. In my University I worked out based on Mass attendance and University statistics of those who ticked “Catholic” for their religion that less than 10% of Catholics attended Mass regularly.
Out of the other races - most Indians are of course Hindu or Muslim, though you will find some are Christian or atheist. For the black people it can really vary from place to place and their tribes. The Xhosa and Zulu have many Christians, and you’ll find that among all the people in SA who are religious blacks are the ones who make up most of those numbers - but that is because they make up at least 80% of the population.
In any case, it is hard to say, because there is a gap between those who identify as Christian and those who actually are Christian. It also depends on where you are. SA is huge, so some areas are very Christian while others not. It also depends on race, and class. On balance, though, I would say that South Africa is a believing nation.