Motorola for phones. Does everything you need with a near AOSP android. Affordable too. good official support, and good community support with lineageos

you should really use FreeOTP+ instead. https://f-droid.org/en/packages/org.liberty.android.freeotpplus/

yes? use it solely for work purposes, at work, turn it off when you clock out…

your employer is not your friend.

≥ and force Microsoft Authenticator on the (private) phones of both employees and volunteers.

Refuse to use the service until they provide you with a work appointed phone. Volunteers admitedly have a more difficult time with that but as someone else said you can indeed do text/call options.