There is such a smartphone. But then you can't use your bank's app because it uses hardware attestation to ban alternative operating systems, and most banks require the app for 2FA or don't have a functional web portal at all. It's going to be even worse once governments roll out age verification apps that use hardware attestation.

Luckily my bank still allows a fob type device as 2FA. But of course your point is valid.

It's a travesty that this behavior is allowed, of course, but as long as it is, I'd keep the cheapest possible regular smartphone around for this purpose alone. I'd try to think of it as an unwieldy fob-like device.