Sonos no longer disable any traded-up devices - so as long as the seller (can in some way) confirm it is working okay at the point of sale (perhaps a recent video of it working), then you should be okay.

If it then transpires it doesn’t work (on receipt) for any reason, your redress would then be with the seller.

Thanks, will see if I can get proof of it working.

As to whether it has already been used for an upgrade, again, you keep need to rely on a screenshot from the seller, showing it is still eligible, and again, should there be an issue, redress it with the seller.