Subscriber is the technical term but really it's donor, because they aren't paying for access to new work product.

Most people who suffer a GoFundMe-type catastrophe don't attract new long-term financial backers over time.

Is it really a grift if the person is upfront about asking for money to pay their medical bills and there's no expectation of a product that isn't being delivered? GoFundMe isn't pretending that there's a laptop or shoes or something expensive and then not delivering aka a scam, it's straightforwardsly asking for money to pay for medical bills.