Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Hello Nekenpongen,
How are you?
As per my knowledge, the MFA is disabled by default. So it is not feasible to enable it automatically for the new synced users.
However, an IT guy provides a workaround that with the Azure AD Premium P2 license assigned, we can use a service named Azure Active Directory Identity Protection, then go to Configuration > MFA registration to create the right settings for your MFA configuration. Enforce Policy and click Save. Please be noted: we have no chance to test it, so if you want to use it, we recommend you test it firstly.
Meanwhile, the bulk updated way for your reference if it is needed.
Also, please submit a feedback to our related team via the Office 365 UserVoice here. You can vote any exist ideas or post a new one there. We would highly appreciate your understanding and efforts.
Regards,
Rudy