How to configure autounattend.xml to handle all Windows updates?

I am using Packer to build an OVA with VirtualBox using a Windows Server 2019 ISO and I am also trying to learn as much as I can about the Windows autounattend.xml files. I have googled and searched this very active forum but can't seem to find anything to point me in the right direction.

So my question is: How does one configure autounattend.xml to handle all Windows updates as the Packer docs recommend?

I have tried System Image Manager to try and find the solution, and I found "Update Services" in "Windows Foundation Package" which might be part of my answer, but when I try to use it I get over 25 validation errors which say a dependency has not been enabled but gives no indication of what dependency I need to enable.

I have also asked on the Packer forum but given I've seen no activity there for the past week even though I've asked other questions there I don't expect to get a response any time soon. But via Google I found this forum which appears to have lots of activity and has had a lot of questions about autounattend.xml so I am hoping I am in the right place.

Thank you in advance if you can help.

There's a packer plugin that will do it
GitHub - rgl/packer-plugin-windows-update: Packer plugin for installing Windows updates

If you specifically want to do it in your autounattend file, you need to run a script that does it for you. The repo I linked has a powershell that can do it. You need to attach it to the vm with floppy_files in your packer file and call it in autounattend like this:

Code:

<SynchronousCommand wcm:action="add">
  <CommandLine>cmd.exe /c C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe -File a:\windows-update.ps1</CommandLine>
  <Description>Run Windows Update</Description>
  <Order>13</Order>
  <RequiresUserInput>true</RequiresUserInput>
</SynchronousCommand>