I have done a lot of work studying and preparing Whonix, and I’ll show just the final steps (it’s been days of work 
).
I got:
virsh # domdisplay Whonix-Workstation
spice://127.0.0.1:5901
virsh # domdisplay Whonix-Gateway
spice://127.0.0.1:5900
virsh #
and that shows I did install something correctly.
However, I have a sans-dbus system, and while I’m fine having Whonix which KDE, which, IIUC has dbus as dependency, I don’t want to install dbus in my system (nor systemd, just to mention).
And my virt-manager is GUI-less. Well, in the sense of it’s own GUI.
Rather, my virt-manager can use virt-viewer instead.
Indeed I have been able to run tails in such sans-dbus virt-manager, with virt-viewer. [1] [2]
The short question is, can virt-viewer be used instead of virt-manager GUI with Whonix?
And the longer question, with the logs, may follow, if there is interest. And very gladly (but patience may be needed, old man here, work slowly).
[1] Tails - virt-manager
https://tails.boum.org/doc/advanced_topics/virtualization/virt-manager/index.en.html
[2] GUI-less (non-dbus) virt-manager (to run Tails in Gentoo)
https://lists.gt.net/gentoo/user/321797