The good thing about standards, is that there are so many of them
The vhdx virtual drive format as used in Microsoft Hyper-V is read-only when used with Virtualbox.
You can however convert the vhdx-file to something writable by Virtualbox.
The conversion
Use Vboxmanage like this.
Using Windows
c:\ > "C:\Program Files\Oracle\VirtualBox\VBoxManage" clonemedium disk /full/path/to/inputdisk/vmdisk.vhdx /full/path/to/outputdisk/vmdisk.vdi --format VDI
Using Linux
# vboxmanage clonemedium disk /full/path/to/inputdisk/vmdisk.vhdx /full/path/to/outputdisk/vmdisk.vdi --format VDI
When you have your vdi-file, use it to create a new virtual machine in Virtualbox, as per usual.
Sources
https://forums.virtualbox.org/viewtopic.php?f=9&t=83990
https://nerddrivel.com/2016/03/14/converting-virtual-machine-disk-formats/
Also see VDI to VHD: Convert Virtualbox vdi-images to Hyper-V vhd.
