My bank warned that they are planning to phase out the code booklet and replace it with a mobile app. Sure, you can continue to use a web browser, but how do you verify anything without a mobile app?
Also, some apps are very picky and refuse to work properly unless your android has GAPPS and is in the in an unmodified state just like the OEM intended. That’s bad news for privacy oriented Android users, let alone anyone who wants to run something even more FOSS.
What if you have appliances such as a scale, lights, watch or something? Pretty much guaranteed that those won’t work unless you use their app. If you want to go FOSS, you may need to sell all of your smart stuff and replace them with similar devices that work in a privacy respecting strictly FOSS environment.