This simple method has worked for me in Windows Server versions 2012 R2 through 2022. Create a new .reg file with the contents below, adjusting the USERNAME, PASSWORD strings as appropriate. Then run it to add to the registry
Windows Registry Editor Version 5.00 [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon] "DefaultUserName"="USERNAME" "DefaultPassword"="PASSWORD" "AutoAdminLogon"="1"
If it is a domain joined machine, then add this line and modify the DOMAIN string.
"DefaultDomainName"="DOMAIN"
Sourced from:
https://community.spiceworks.com/topic/1911274-autologin-autologon-sysinternals-with-windows-10-issue#entry-6360895
More information on this method:
https://docs.microsoft.com/en-us/troubleshoot/windows-server/user-profiles-and-logon/turn-on-automatic-logon