It's not the same for every bank. Now I have (still) stock XZ2 but before that I had moto x play with custom ROM (AOSP extended), so, rooted, no sign of google on it (I was using f-droid and yalp) and my app which I mostly used just to get an authentication code and then the rest in the browser was working just fine. And bank is part of intensa sanpaolo group so not something small and local.