Rivian does not provide a free trial of Tidal. Tidal will provide a 30 day free trial of their HiFi product. Tidal does not provide a free version of their service via the app in the Rivian vehicle, but will via your phone's app. I had 12 email exchanges with Tidal support, and a couple with Rivian support, while investigating / troubleshooting. Tidal support was awful, clueless, and completely turned me off from even considering their product.
Tidal's current free trial offer is for 30 days. Not provided by Rivian but a free trial is a free trial. Or there is the 3 month trial for $1 through Best Buy as linked above.