Licensing and Onboarding Servers in 365 Defender for Endpoint

Hello all,

We are in the process of onboarding all our servers to 365 Defender for Endpoint. Here's a brief overview:

• Total servers: ~170
  • Windows: 80 (Ranging from WS2012R2 to WS2022)
  • Linux: 90
• Current status: 40% onboarded during our experimental phase, but they are without licenses. They are onboarded with MDE direct onboarding via GPO.
• We are currently using 365 Defender for Endpoint for all our Windows 10/11 workstations with an M365 E3 license.

Our primary questions are:

1. What specific license do we need to onboard all our servers to 365 Defender for Endpoint?
2. Is it necessary to have a license in place before onboarding, or can we purchase the license afterward?
3. How do we assign these licenses? Will the servers automatically be allocated a license upon onboarding, or is there a manual process involved?

Any guidance or insights would be greatly appreciated. Thank you!