Hey, I think it would be a good idea for Revolut to partner up with barzahlen.de,
Barzahlen is partner with most major drug and supermarkets in Germany, including big names such as dm, rewe, edeka and much more
They are also partners with places in Austria such as BILLA
Barzahlen allows you to deposit money in your card by just going to a cashier and showing them a barcode and simply paying! You can also withdraw money that way.