The FSCA does not prohibit bonuses, so brokers operating legally in South Africa can and do offer them. What the FSCA does require is licensing: a retail forex or CFD broker needs a Financial Services Provider (FSP) authorisation, and since 2019 it also needs an Over-the-counter Derivative Provider (ODP) licence to offer derivatives to South African clients.
Because bonuses are allowed, South Africa sees most of the global deposit-match and no-deposit promotions that the EU and UK block. The trade-off is that the burden falls on you to confirm the broker is properly licensed before you chase a headline number.
Before claiming any offer, check the broker's FSP number on the FSCA website. A large bonus from an unlicensed or offshore-only broker is worth far less than a modest one from a broker that is authorised to take South African clients and will actually let you withdraw.