I've tried installing and booting both Whonix 13.0.0.1.4 and Whonix14.0.0.2.6, downloaded and verified from Whonix's onion mirror. In both cases and with both VMs I got this same result. A black screen with "Booting from Hard Disk... Boot failed: not a bootable disk. No bootable device."
To install them I followed this guide (https://www.whonix.org/wiki/KVM), the only thing I've done differently is to download alternative packages for libvirt-bin, as suggested by apt:
[sudo] password for thoreau:
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package libvirt-bin is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
However the following packages replace it:
libvirt-daemon-system libvirt-dev libvirt-clients
E: Package 'libvirt-bin' has no installation candidate
thoreau@Thoreau:~/Installers/Whonix$
And that's it. I'm stuck and don't even know what seems to be the problem. If there's any more information that I could provide, please ask.