Why not launch a new startup focused on building an open smartphone? This is HN after all, with the right pitch someone will throw money at it.
Because only a bunch of nerds would use it, your bank wouldn't support running its shitty app on it, and it's back to square 1.
Because only a bunch of nerds would use it, your bank wouldn't support running its shitty app on it, and it's back to square 1.