If Generation 2, must disable Secure Boot
Get-VM | Get-VMFirmware
Get-VM -Name 'TrustyTahr' | Set-VMFirmware -EnableSecureBoot Off
https://blog.couchbase.com/hyper-v-run-ubuntu-linux-windows/ https://docs.microsoft.com/en-us/windows-server/virtualization/hyper-v/supported-ubuntu-virtual-machines-on-hyper-v