They have about 25 million customers, which would be about 5% of the EU population. Meanwhile about 38% of Europeans own a credit card [1].
Revolut is growing rapidly, so I assume there are plenty of bubbles where revolut is more widespread than credit cards. But the near-universal scheme in the EU would be sepa direct debit. And while the lack of instant confirmation is a drawback for online purchases, that shouldn't matter for something like GitHub Sponsors.
