OneDrive Sync for Azure AD Joined Computers

JWat12 

The answer I got from Microsoft is that you need to have the devices AD joined or hybrid joined or you need to use Conditional Access Policies.

Rather than using the OneDrive Sync policy they said to use a different one. In the SharePoint Admin Center go to Policies, Access Control. The Unmanaged Devices policy allows you to block access for unmanaged devices. It defines unmanaged devices as ones that are either hybrid AD joined or Intune managed.

At first I thought this would work for us. All our AAD joined devices are Intune managed and it would be easy enough to hybrid join the rest. However, here is where Microsoft tries a scam. I doesn't say on the Unmanaged Devices Policy page but enabling this requires that every user the policy applies to needs to have an AAD P1 license. Of course there is a good chance that you won't realize that until a year later and MS comes back and asks for payment for all the licenses you need but they don't tell you. 

In our case, it would mean purchasing AAD P1 licenses for the 95% of our people who use computers that aren't AAD joined which doesn't make sense for us.