Yes I agree on Best Buy. I’ve also gotten lengthy trials through Target Circle (their free “vip” membership level) and T-Mobile (my mobile carrier). I think I was able to get more than one round from each, but I was disappointed when they finally started telling me “you’ve already used this offer”. And I bought my latest iPhone near the beginning of Covid, when they kept extending the free trial for many months. So with a few breaks, I’ve had almost 5 years of Apple TV+ but probably only paid for less than a year.
I’m sure they’re not as generous now, but try googling for offers if you haven’t already.