POD: The original settlement destined for France Antarctique decides to settle at the Cape of Good Hope in 1555 instead. It doesn't end up being destroyed by the Portuguese the way France Antarctique did in OTL and is joined by the settlers that in OTL went to Fort Caroline in Florida and were slaughtered by the Spanish. While it starts of Huguenot, Catholics do end up moving there as well, and the colony is allowed to be religious tolerant due to its Huguenot foundings with more French Protestants settling there after religious tensions in France proper.
How would a French South Africa develop after the initial founding of Fort Coligny (OTL Capetown) in the 1550s?