My bank only has two options for authentication: Either you use their mobile app or buy an authentication device from them that's the size of a small phone. Either way I need a handheld device.
I can't say I'm happy with the direction of things. They used to offer slips of paper with single-use codes that worked fine, but those are now deprecated in favor of the smartphone app.
Then your bank is garbage and you should switch to a better one. My main bank (USAA) lets me use a one time code sent to my email as a second factor (or SMS, or a code from their app). If they started requiring me to use the app I would drop them immediately. Why is "but my banking app" treated like a valid objection every time user freedom comes up?
Because it's most banks that are like that. If you don't have this problem, then you're lucky your bank is actually technologically incompetent by industry standards.
You can use a lot of those authentication / bank apps on a tablet without issue. Obviously it’s worth verifying before making the swap to a flip phone, but I like having minimal apps on my smartphone so I still have a backup if needed.
I can't say I'm happy with the direction of things. They used to offer slips of paper with single-use codes that worked fine, but those are now deprecated in favor of the smartphone app.