Dism /Online /Get-TargetEditions
Dism /online /Set-Edition:ServerStandard /AcceptEula /ProductKey:12345-67890-12345-67890-12345
Windows Server 2019 Standard:
DISM /online /Set-Edition:ServerStandard /ProductKey:N69G4-B89J2-4G8F4-WWYCC-J464C /AcceptEula