From the SB website (not the app) search the Shop section for Best Buy. On the store page there's an option for a bonus if you buy from the weekly ad or shop in store. It's a sliding scale, a 50-99 purchase gets 250sb, 100-499 purchase gets 750sb, and 500 and up is 1500sb. This is a bonus on top of the % back you get from shopping, currently at 2%. The fine print excludes gift cards, however, in practice it pays out on GC purchases. Click on the box for the instore bonus and it'll give you a QR code to have the cashier scan, that's how it tracks your purchase to pay out on your SB account. Make sure it's scanned before they total the order for payment. (You'll see it on your receipt) The 2% sb goes pending for the normal 30ish days, but the bonus is paid out when it gets picked up, usually the same day but is occasionally delayed a day or two.
You can combine it with BB rewards points and, as mentioned in the PP, this quarter for Chase Freedom Chase Pay is part of the 5% categories which BB is one of the few places that takes Chase Pay. I give the cashier our BB rewards number, have them scan the SB QR code, ring up the GC, then have them scan the Chase Pay QR code to pay. If you can buy in $100 increments that gets your best return now. Can only do one transaction per day for SB. I did this last Friday, the trip went pending over the weekend, got the bonus on Monday (bonuses are only paid out on business days, just a quirk).