Nobody said consumer fintech? You can just operate as a business. "Sole proprietor" is a real thing that almost every service knows how to deal with, and if one can't there's a competitor willing to right next door.
Yes, you can go get a personal loan, or a retail banking account, or a personal payment processing account, but as I said, you're going to be locked out of a lot of B2B products.
Example, since you edited to add examples: I have several business bank accounts and far too many Stripe accounts all registered as sole prop. I haven't had to take a loan but I do have a sole prop credit card. My understanding is that even with an LLC a bank is going to require a personal guarantee for a loan.