Yes, some have.
In order to deliver money as quickly as possible to those who need it, the IRS is sending stimulus payments to eligible taxpayers who filed a tax return in either 2019 or 2018 and chose to receive their refund via direct deposit into their checking account. These taxpayers will automatically have their stimulus payment deposited into the account they received their refund.
We have not yet received confirmation from the IRS on whether they will be putting stimulus payments on prepaid debit cards. However, we have noticed that the IRS has started depositing stimulus payments on some prepaid debit cards for taxpayers that chose to receive their refund through that method in tax year 2019 or 2018