Not "we could not find any." We looked, and the shelf is empty. Here is the evidence, so you can decide whether that is an opportunity or a warning.
The central bank policy rate is 7.00% (Repurchase rate (repo rate); prime lending rate 10.50%). source
ZAR, empty. ZARP exists as a rand stablecoin; searches for rand-denominated on-chain yield returned nothing but generic DEX liquidity-mining content.
An empty shelf in a currency with a real policy rate is a gap between what savers are owed and what they can reach. It closes when someone with the licence to hold the underlying paper is willing to put a claim on it on-chain. Until then, holders of ZAR choosing to earn are choosing to hold a different currency, whether they have priced that decision or not. The calculator prices it.
See every currency or read how we establish that something is absent.