A card terminal is no longer the only way to take a payment at the counter. Bank-to-bank payments reach your account directly, and customers approve them in the banking app they already trust.
A printed QR code at the till, a Paylink sent by text, a Request to Pay for an invoice, a dynamic QR on a delivery docket and a payment button on your website all work without extra hardware.
Start with the one that matches how your customers already buy from you, then add the others as you need them.