My work requires that I use Microsoft Authenticator on my personal cell phone, to log in to my work account (very frustrating and unfair imo… but that’s a different topic).
Has anyone been able to sideload these kinds of apps to a dumbphone? If so, how well does it work and what kind of dumbphone do you use? I currently have an iPhone and I’m becoming increasingly frustrated with Apple and want to get away from them.

The Microsoft app doesn’t use standard 2FA method. You have to use their app. Of course!