Activation Threshold: KMS requires a minimum of 5 servers or 25 workstations to be "checked in" before it begins activating clients.
Firewall: Port 1688 (TCP) must be open on the KMS host to receive requests. windows server 2019 kms iso link
Microsoft Evaluation Center: If you are testing the OS, you can download the 180-day evaluation ISO. Note that evaluation versions must be converted to the full version via a DISM command before they can be activated via KMS. Activation Threshold: KMS requires a minimum of 5