Confirmed...
The dates are listed at https://learn.microsoft.com/en-us/entra/identity/authentication/concept-mandatory-multifactor-authentication and they do include the Entra admin center, the Intune Admin center, and the Azure portal.
Security defaults would apply if you don't use P1 or P2 licensing (with Conditional Access). As per the aforementioned article:
If your organization chose to retain Microsoft’s security defaults, and you currently have security defaults enabled, your users don't see any changes as MFA is already required for Azure management. If your tenant is using Conditional Access policies in Microsoft Entra and you already have a Conditional Access policy through which users sign into Azure with MFA, then your users don't see a change. Similarly, any restrictive Conditional Access policies that target Azure and require stronger authentication, such as phishing-resistant MFA, continue to be enforced. Users don't see any changes.
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hth
Marcin