Here's how it works:
If you filed a 2018 and/or 2019 return with the IRS, and at least one of those returns had a refund which was direct-deposited, the IRS will deposit your stimulus payment into that account (if it's closed, you'll get a check instead.)
If you filed a 2018 and/or 2019 return and neither one had a refund coming, the IRS will mail you a stimulus check. The same holds true if these returns had a refund which was sent as a check.
In other words, if you requested a direct-deposited refund on at least one return in the past two years – 2018 or 2019 – your stimulus will be direct-deposited into that account (assuming it's still valid), and if not, you'll get a check. This cannot be changed.