How can I use a debit card to pay my Apple Card?

Debit cards are used to fund your Apple Cash account. You Apple Cash Account must be verified first. Link how is below.

Once the Apple Cash account is verified and loaded with cash from your debit card, use Apple Cash in Wallet to pay you Apple Card account.

Please see links,

https://support.apple.com/en-us/HT207887

https://support.apple.com/en-us/HT209226

If you choose Pay Now, you can use your Apple Cash balance to make an immediate one-time payment. If the balance of your Apple Cash account is less than the amount of your payment, the remaining balance is paid from your default bank account.

You can also choose a different bank account to pay your Apple Card balance:

1. Open the Wallet app on your iPhone and tap Apple Card.
2. Tap to pay.
3. Choose a payment amount and tap the Pay Now button.
4. Tap your bank account, then choose a different bank account.
5. Tap the Back button and authenticate with Face ID, Touch ID, or your passcode to make a payment.

You cannot. You must use the methods in the link you referenced. For any other methods you must call Goldman Sachs at 1.877.255.5923 and work something out.