Sirius XM is currently offering their select subscription free for 2 months for “pre-owned” vehicles that do not have a current subscription. This works even if you have had the vehicle since new. If you paid for a subscription at some point or used a similar deal in the past you may have to use a different e-mail address, physical address, phone number etc. then previously used for that specific radio. Physical address must be a valid address in the US. Credit Card is not required.
Some people have gotten lucky and gotten a confirmation showing 4 months free after applying.