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Coinbase isn't available to US citizens so far IIRC, only Europeans, and the original poster clearly said he lives there.
Who can sign up for a Coinbase Card?So he/she can't.
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Don't worry the UnionPay cards aren't massively accepted in Europe, with P.O.S it's ok but not all ATMs accept UnionPay network. I believe the problem in Africa is its ecosystem since I know the majority of transactions are done with cash (a lot of unbanked persons, not everyone internet access, etc...)
I suppose it will work, for example, there are Bank of Africa or Ecobank available in many African countries and providing Mastercard...
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What do you mean by saying "a good card accepts Visa and Mastercard"? It's only a Mastercard by the way. And we need to join a waiting list and referer people if we want to get it faster.
If you wanted to mean a we can top up the card with another Visa/Mastercard then it's out of topic