Re: how to allow specific Android manufacturer to enroll device and block all others.

Yes, you have to add the manufacturers that you want to block not the opposite. Honestly, I’m not sure if this ever be added to the roadmap.

Hope this helps!
Moe

Here is a link for the roadmap:

https://docs.microsoft.com/en-us/mem/intune/fundamentals/in-development

Android Restriction:
https://www.inthecloud247.com/block-android-enrollments-by-device-manufacturer-in-microsoft-intune/