According to ABRA, select prepaid debit cards can be used to purchase BTC. i wish i had known about this last year when i tried every which way to buy crypto with a prepaid debit, before ultimately giving up. Hopefully this info is helpful to someone in the future. You can add money to your Abra Wallet using the following Eligible U.S. American Express Cards: Any valid (1) American Express Consumer Card issued by American Express, (2) American Express Card issued by a licensed third-party licensed to issue American Express-branded Cards and (3) registered American Express general purpose reloadable prepaid cards* including American Express Serve® and Bluebird® cards. *Prepaid cards require a positive balance before the card(s) may be added in-app.