Do I need to provide my mobile phone number to set up MFA?


It depends on the authenticator app you choose.  Both the Google Authenticator and RapidIdentity apps that run on your mobile device use a time-based one-time password (TOTP) algorithm to provide a valid 6-digit code (it is not texted to your phone), so while the application RUNS on your phone, you are not sharing the number with anyone nor being changed any fees.  However, Authy (one of the alternate authentication apps that runs on your desktop), requires that you enter your cell number when installing and registering the application with the vendor.