issues:
Failed to open a session for the virtual machine ubuntu.
Raw-mode is unavailable courtesy of Hyper-V. (VERR_SUPDRV_NO_RAW_MODE_HYPER_V_ROOT).
Resul
For me the combination of the following three was the solution:
1. control panel > turn windows features on or offf > Hyper-V : deselect
2. admin cmd > bcdedit > hypervisorlaunchtype:Auto disabling: bcdedit /set hypervisorlaunchtype off
3. gpedit.msc > 'Computer configuration > Administrative Template > Device Guard' > Turn On Virtualization Based Security : Change from 'Not configured' to 'Disabled'
REBOOT
note: after the reboot the VirtualBox worked, but Docker Desktop's VirtualBox started complaining about missing Hyper-V !
It seems that this might have been the root of all my evil... Extra info: https://forums.docker.com/t/running-docker-and-virtualbox-on-the-same-machine/23578/13