Because of this currently building Whonix VirtualBox from source code is also broken.
An awful, not great solution for future Whonix VirtualBox development might would be to install VirtualBox from Oracle Repository and then try make VirtualBox guest additions from ISO work and pre-install / automate that.
Related:
- Installation of VirtualBox guest additions from ISO might also cause issues.
- nonfree vs freedom:
- VirtualBox forums question: Is VBoxGuestAdditions_6.1.10.iso OSE or PUEL?
- Debian bug report: move virtualbox-guest-additions-iso from non-free to contrib
- VirtualBox bug report: clarify license of VBoxGuestAdditions ISO OSE or PUEL (free vs nonfree)