I would like to ask if it is safe to add another repository (e.g. kali) to Whonix Workstation (Qubes-Whonix), whether the whole security of Whonix Workstation will be weakened? Or is it better to use pure debian and not change Whonix Workstation at all? If you don’t recommend adding anything to Workstation, why?
See: Foreign Sources
(Whonix is based on Kicksecure.)
is generally very much on the topic.