Could also be a manual copy/paste of the contract address, ether and gas amount to your native wallet app, or a QR code to take a picture of with a mobile walle

Could also be a manual copy/paste of the contract address, ether and gas amount to your native wallet app, or a QR code to take a picture of with a mobile wallet. Metamask (the browser plugin) is one - albeit a bit clunky in terms of UX - way of reducing the friction of doing web based ethereum payments, separated from your main wallet