Hi @ARCC Admin • Thank you for reaching out.
Unfortunately, it is not possible to turn off MFA for specific user(s) when Security Defaults is enabled. Enabling Security Defaults in a tenant enables MFA for all users in that tenant. As it is a free offering, there is no fine grain control.
This can be done either via Conditional Access Policy or Per user MFA, which requires assigning required licenses to all the users leveraging Azure MFA.
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