Hi Susan,
If the Microsoft 365 Nonprofit offer includes Azure AD Premium 1 or Premium 2 licenses then you can enable the alternative MFA methods for phone or text. To accomplish this you'll need to do disable the "Security Defaults" setting in Azure AD and enable Conditional Access policies.
To disable security defaults in your directory:
- Sign in to the Azure portal as a security administrator, Conditional Access administrator, or global administrator.
- Browse to Azure Active Directory > Properties.
- Select Manage security defaults.
- Set the Enable security defaults toggle to No.
- Select Save.
Next you'll need to create Conditional Access Policies. Refer to the following article for more details.
https://learn.microsoft.com/en-us/azure/active-directory/authentication/tutorial-enable-azure-mfa
Hope that helps you,
Travis