I’m not sure what’s happening on AliExpress but searching for RAK831 or ‘RAK LoRa’ only comes up with a store called ‘Smile with me’ with very high prices (60+% higher) for the RAK (gateway) products (nothing to smile about).
For those interested in RAK Wireless products, use this URL for the ‘RAK Wireless Module Store’ on AliExpress: https://www.aliexpress.com/store/2805180