Not sure if mentioned before, if you open up your Apple TV Plus app on your Samsung TV, if your TV is eligible you will see the option to get 3 months free.
Mine is 2022 Samsung The Frame, I am still eligible, my previous free trial expired yesterday, I have no problem to re-subscribed to it again.
No harm to try if you don't have an active Apple TV Plus subscription.
Will this also work if you activate it on the demo TVs in-store?