I seem to experience this issue in a current fully updated Whonix15. The machine starts to boot, and then reaches a screen that remains black and does not proceed. I have tested a separate Debian VM and it works with VMSVGA and 3d enabled.
Virtualbox version 6.1.4
Guest additions 2 packages from Debian repo: virtualbox-guest-dkms, and virtualbox-guest-utils
Debian Buster host machine, also up to date. Kernel 4.19.0-8amd64
2 Likes