WinPE was recently upgraded per KB 150348.
While trying to install Windows Server 2019 Datacenter, the install fails immediately with the error Windows could not apply the Windows PE bootstrap specified in the unattend answer file. Afterwards, the drive was checked and it never even got to the point of formatting, which is done via an answer file.
Deployment Solution 8.x
The error: Windows could not apply the Windows PE bootstrap specified in the unattend answer file happens when there are incorrect settings in the Unattended XML file. In this case the Boot Drives listed in the XML was incorrect as was the License Key that was not for the intended Windows Server version (2019 Datacenter) but instead was for the Standard version. After resolving these two issues the image was successfully deployed.
150348 Installing WinPE10 ADK for use in Deployment Solution 8.x