You can use the majority of the banking apps without a Google Account on an Android through the Aurora Store:

* https://f-droid.org/packages/com.aurora.store/

I've tried it, it works.

With Apple, it's all far worse. On iOS, I've discovered that even some preinstalled premium apps, like Pages, Numbers, Keynote, GarageBand, iMovie, don't work unless you add an Apple Account to the system.

But with Android, it's relatively easy to set it up without any accounts, through Chrome, F-Droid, Aurora Store. (And I usually uninstall Chrome after installing F-Droid, too.)