Thank you for reporting this! We have tracked down the issue and are working on a fix. I have blogged the details here: https://american-boffin.com/2019/01/17/virtual-machines-do-not-boot-after-moving-from-windows-server-2012-r2-to-windows-server-2019/
This script should help you out: https://github.com/BenjaminArmstrong/Hyper-V-PowerShell/tree/master/Image-Factory
Can you provide more details? It is possible to configure the VLAN for the host OS on a vSwitch using Hyper-V Manager today.