This isn't me shilling the card, but I guess it's 15% off on your first purchase or day of having the card? That being said, the rewards are best buy points so that does limit things.
https://www.bestbuy.com/site/misc/financing-rewards/pcmcat102500050032.c?id=pcmcat102500050032
15% back in rewards:
*Offer valid 6/2/25–7/6/25. Get 2.5 points per $1 spent (5% back in rewards) on qualifying Best Buy purchases when you choose Standard Credit with your My Best Buy® Credit Card. If you apply and are approved for a new My Best Buy Credit Card, your first day of purchases on the Credit Card using Standard Credit within the first 14 days of account opening will get an additional 5 bonus points (an additional 10% back in rewards, for a total of 15%).