You still haven't answered their question.
Which bank?
I don't know the bank they are referring to, but I can cite an example for me: RBC Royal Bank of Canada requires the mobile app. There is nothing you can do on their website without first 2FA via their specific mobile app, and even then only in limited transaction sizes. If you want "full access" (e.g. up to $10k daily transfer via e-transfer) then you MUST use biometrics and the mobile app.
There is also an alternative for now, but nothing as simple as SMS or authenticator app. They give you a special credit card shaped card with a card reader that you can use to authenticate with using your PIN, which is mostly considered legacy now with the bank app. It's also not realistic to be carrying this thing around everywhere either as it's bigger than my phone.
There is also a national ID app that is used everywhere that I'm worried will stop working on GrapheneOS... Because without it I won't even be able to access online government services like healthcare, taxes, etc.