In Germany, traditional banks and credit unions offer a financial API called FinTS [0]. A couple of desktop banking apps support FinTS, and consumers can typically use it free of charge.
The API has been around since 1998 and is one of the best pieces of software ever produced in Germany imho (if we ignore for a second that that bar is pretty low to begin with).
Unfortunately, it’s mostly traditional German banks and credit unions that offer FinTS. From a neobank’s point of view, chances are you’re catering to a global audience, so you just cobble together a questionable smartphone app and call it a day. That’s probably cheaper and makes more sense than offering a protocol that only works in Germany.
I wish FinTS had caught on internationally though!