Couldnt reproduce on my debian host:
user@host:~/Downloads$ tar -xvf Whonix*.libvirt.xz
WHONIX_BINARY_LICENSE_AGREEMENT
WHONIX_DISCLAIMER
Whonix-Gateway.xml
Whonix-Workstation.xml
Whonix_external_network.xml
Whonix_internal_network.xml
Whonix-Gateway-Xfce-17.2.3.7.Intel_AMD64.qcow2
Whonix-Workstation-Xfce-17.2.3.7.Intel_AMD64.qcow2
user@host:~/Downloads$ sudo virsh -c qemu:///system net-define Whonix_external*.xml
[sudo] password for user:
Network Whonix-External defined from Whonix_external_network.xml
user@host:~/Downloads$ sudo virsh -c qemu:///system net-define Whonix_internal*.xml
Network Whonix-Internal defined from Whonix_internal_network.xml
user@host:~/Downloads$ sudo virsh -c qemu:///system net-autostart Whonix-External
Network Whonix-External marked as autostarted
user@host:~/Downloads$ sudo virsh -c qemu:///system net-start Whonix-External
Network Whonix-External started
user@host:~/Downloads$ sudo virsh -c qemu:///system net-autostart Whonix-Internal
Network Whonix-Internal marked as autostarted
user@host:~/Downloads$ sudo virsh -c qemu:///system net-start Whonix-Internal
Network Whonix-Internal started
user@host:~/Downloads$ sudo virsh -c qemu:///system define Whonix-Gateway*.xml
Domain 'Whonix-Gateway' defined from Whonix-Gateway.xml
user@host:~/Downloads$ sudo virsh -c qemu:///system define Whonix-Workstation*.xml
Domain 'Whonix-Workstation' defined from Whonix-Workstation.xml
user@host:~/Downloads$ sudo mv Whonix-Gateway*.qcow2 /var/lib/libvirt/images/Whonix-Gateway.qcow2
user@host:~/Downloads$ sudo mv Whonix-Workstation*.qcow2 /var/lib/libvirt/images/Whonix-Workstation.qcow2
user@host:~/Downloads$
For opensuse tumbleweed better to contact your support to find out which package you are missing to install. probably command could be like this:
sudo zypper install qemu qemu-kvm libvirt-daemon libvirt-daemon-qemu spice spice-client spice-protocol spice-vdagent
Then restart libvirt:
sudo systemctl restart libvirtd
See if it will works out with you.