A notable mention is https://ubports.com/en/ which is different from postmarketos in a sense that ubports uses old kernels with heavy patches. That means: good support for things, but difficult future.
PostmarketOS uses the newest kernels and tries to integrate their patches into mainline kernel, so that the reliability is maintained with all kernel developers.
Actually, what is hard about changing banks? I give my bank info to as few entities as possible. And almost all of them would take a few clicks and possibly a few days to verify some tiny transaction and I would be done. Changing credit cards is far harder. But also. Why are you using the banks app on your phone. That phone is probably the least secure electronic you own. The attack surface on that thing is absolutely huge.