Assigning Microsoft Defender for Endpoint (DFE) Licenses to Devices Without a Cloud-Visible User

We have a number of Windows 10 and Windows 7 clients that are used to control production systems. These devices do not have a cloud-visible user, as they are not associated with an Entra ID (Azure AD) account. However, each device does have a local Windows user for system operations.

The challenge we are facing is how to assign Defender for Endpoint (DFE) licenses to these devices, since DFE licensing is primarily user-based, and there is no direct device-based licensing for client OS.

Our main questions:

How can we assign a newly purchased DFE device license to a client that has no user?
Is there a way to assign licenses to local Windows users even if they are not synced to Entra ID?