The rental market analogue of a dark pool is the rental market. All transactions are secret by default, allowing higher-information parties (landlords) to set prices that are advantageous to them, and prevent transactions from moving the market.

These algorithmic pricing systems extend that information advantage by pooling information across landlords (maybe not illegal by itself) and leveraging their position as market-wide price-setter to push rents higher, with the promise that so many units are following their recommendations that renters have ~no alternative (very illegal price fixing)