So my company decided to migrate office suite and email etc to Microsoft365. Whatever. But for 2FA login they decided to disable the option to choose "any authenticator" and force Microsoft Authenticator on the (private) phones of both employees and volunteers. Is there any valid reason why they would do this, like it's demonstrably safer? Or is this a battle I can pick to shield myself a little from MS?
Can you claim that you don't have a smartphone? Then they'd either have to provide an alternative authentication method, or provide you with a phone.
I've been part of the Microsoft Bad crowd for well over 25 years now, but there are a few things that I will concede that MS has done well. Authenticator is one of them. I haven't looked much into the privacy aspect of it, though.
Don't do that. Just say they will provide you with an authenticator paid for by them.
I did this at my work and got a little dongle that displays a string of numbers I have to enter when prompted.