These files are very similar to the Managed Identity and show the difference in authentication. (Only difference is that the use_azure_cli_auth = true is omitted.)
These require a managed identity (system or user assigned) on a server (e.g. a config management server) which has Contributor access on the subscription, or on specific resource groups.
packer build ~/packer/auth/managed_identity/ubuntu_focal_gen2.pkr.hclCreates image ubuntu_focal_gen2 in resource group images.
imageId=$(az image show --name ubuntu_focal_gen2 --resource-group images --query id --output tsv)