Thank you for the response.
I checked that the file exists in the Deployment Share, ran a complete regeneration of the Deployment Share in Deployment Workbench , updated the Boot Image in WDS, restarted the WDS service and re-tried a deployment of Enterprise 21H1. The same error occurred in the Inject Drivers phase.
During the re-generation, there were a number of driver related errors (see example below).
Installing 1 of 1 - E:\DeploymentShare\Out-of-box Drivers\Net\net8187b_62.1182.0331.2010_B046BD4F8C88E09577AB8151633F255E7A1D5016FDC2B25D4109109C211BE2B3\net8187Se.inf:
INFO: DISM has skipped driver signature check because the version of running OS and that of target OS do not match.
Error - An error occurred. The driver package could not be installed.
For more information, check for log files in the <windir>\inf folder of the target image.
The system cannot find the file specified.
The DISM log file can be found at C:\Windows\Logs\DISM\dism.log