Have yoz really checked for GrapheneOS? Which country?

Is using a cheap Android device (the cheapest Android phones are less than $100 on Amazon) an option? The idea is to use that phone for 2FA or whatever is app is necessary for, and use a degoogled device for your other day-to-day activities. It's not ideal because you need to spend some extra money, but it buys you a lot of privacy.

Does the web app for the bank actually selectively block mobile phones? I just checked and Chase here in the US lets me log in on Brave Mobile on iOS. Perhaps your bank lets you log on in the browser.