If you don't want a store-branded card — or you can't get Prime — a general 2% cashback card earns on Amazon and every other retailer with no bonus categories to activate and no spending caps to plan around.
Pick a card with a flat rate of 1.5% or 2% on all purchases (Citi Double Cash, Wells Fargo Active Cash, Fidelity Rewards Visa, SoFi Unlimited 2%).
Use it as your default card for Amazon and everywhere else.
Redeem earned cashback as a statement credit, direct deposit, or brokerage deposit depending on the issuer.
Shoppers who split spending across many retailers, don't want another Prime-linked product, or already have a Prime Visa and want a backup card for non-Amazon spend.
Flat 2% loses to the Prime Visa's 5% on Amazon itself. Use one of these as your everywhere-else card, not necessarily your Amazon card.