How can I force windows 10 desktop logins to use Azure MFA? It seems that the new release of Windows 10 includes an option for web sign on, and if you have have the PC joined to to Azure AD, then it seems like it might work this way.
If so, then how can you force a Windows 10 PC to join an Azure AD via Remote Desktop? That option isnt available throught the normal process of: start -> settings -> about -> join Azure AD
I had the same question (How do I enforce AzureMFA for an AzureAD-joined Windows 10 Workstation?). At this time, I do not think it is supported.
For reference, there's more than 1,000 votes for the Azure feedback item Add MFA support to Secure the Windows 10 logon.
You can enable conditional access to enforce MFA. This is done at the user level and requires Azure AD premium (P1 and above).