What makes you think you necessarily need a separate account at an exchange? Theoretically Brave could offer to pay you via pretty much any method you want. (Direct deposit, Paypal, Bitcoin, BAT, or yes, even a check in the mail if you prefer.) They just need a way to verify that they're sending the money to the right person; it's not like they already have your address.
Randomly accepting money from strangers is a bit of a compliance nightmare. You don’t want to chair a charity that winds up having received donations from sanctioned persons.
