Is it a new account? Or is it just a new debit card number that references the same checking account?

With credit cards it’s a bit more obvious what’s going on because there’s a clear difference between closing an account (requires another credit check), cancelling a card (changes number, but doesn’t change underlying account), and reissuing a card (same number, just replaces the physical card). I’ve done all three with debit cards, and at least here, cancelling a card just means those numbers are no longer valid and you’ll get new numbers, but the account is in-tact (and you retain the same account number) and autopay is redirected to the new number automatically.

I haven’t had a debit card replacement impact the account except one time, when the checking account number was embedded in the debit card number (small bank, never again), and that was like 15 years ago.