Hi,
Microsoft 365 E3 does include rights to Windows Virtual Desktop, but that is a service hosted on Azure.
Looks like you need to configure VDA for Windows 10 Subscription Activation Requirements.
This document describes how to configure virtual machines (VMs) to enable Windows 10 Subscription Activation in a Windows Virtual Desktop Access (VDA) scenario.
https://learn.microsoft.com/en-us/windows/deployment/vda-subscription-activation
Best Regards,