I don't know where you are, and I'm not an expert, but a job requiring specific technology typically means it is your employer's responsibility to provide that technology. So if they signed a contract that mandates you have a smartphone, you can use your own if you like, but I think they are legally required to provide you with one if you choose not to buy one. In fact in most cases, I think they should prefer that (since the security of your personal device is very much none of their business).

I think this is kind of a ticking time bomb with a lot of companies depending on personal devices for 2FA.

They might be a student, in which case the rules might be much less in their favor.

"après moi le déluge" - said every public sector purchase decision maker ever.