Comment # 4 on bug 1177763 from Peter McDonough

Last first:

from Tumbleweed /root/.cache/virt-manager/virt-manager.log

as root:
lux-tw:~ # ls -la ~/.cache/
insgesamt 1356
drwx------  3 root root     4096  9. Okt 22:31 .
drwx------  9 root root     4096 20. Okt 11:36 ..
-rw-r--r--  1 root root 10547304 19. Okt 21:49 icon-cache.kcache
drwxr-xr-x 43 root root     4096 12. Okt 12:08 mesa_shader_cache

There is no virt-manager/virt-manager.log. (!)

I did nothing complex with virt-manager, 
just plain Tumbleweed plasma and standard kvm + tool from Yast

Start with virtual manager and

" The libvirtd service does not appear to be installed. ..."

I did the same in leap 15.2, no problem.
The difference I can see between both and I suspect there is the root of the
problem

with rpm -qa libvirt\*

Yast pulls in Leap 15.2 - 26 packages
in Tumbleweed only - 22 packages, check below:

lux-tw:~ # rpm -qa libvirt\* 
libvirt-glib-1_0-0-3.0.0-1.3.x86_64
libvirt-bash-completion-6.8.0-1.1.noarch
libvirt-libs-6.8.0-1.1.x86_64
libvirt-client-6.8.0-1.1.x86_64
libvirt-daemon-6.8.0-1.1.x86_64
libvirt-daemon-driver-storage-core-6.8.0-1.1.x86_64
libvirt-daemon-driver-secret-6.8.0-1.1.x86_64
libvirt-daemon-driver-qemu-6.8.0-1.1.x86_64
libvirt-daemon-driver-nwfilter-6.8.0-1.1.x86_64
libvirt-daemon-driver-nodedev-6.8.0-1.1.x86_64
libvirt-daemon-driver-network-6.8.0-1.1.x86_64
libvirt-daemon-driver-interface-6.8.0-1.1.x86_64
libvirt-daemon-driver-storage-scsi-6.8.0-1.1.x86_64
libvirt-daemon-driver-storage-rbd-6.8.0-1.1.x86_64
libvirt-daemon-driver-storage-mpath-6.8.0-1.1.x86_64
libvirt-daemon-driver-storage-logical-6.8.0-1.1.x86_64
libvirt-daemon-driver-storage-iscsi-direct-6.8.0-1.1.x86_64
libvirt-daemon-driver-storage-iscsi-6.8.0-1.1.x86_64
libvirt-daemon-driver-storage-disk-6.8.0-1.1.x86_64
libvirt-daemon-config-network-6.8.0-1.1.x86_64
libvirt-daemon-driver-storage-6.8.0-1.1.x86_64
libvirt-daemon-qemu-6.8.0-1.1.x86_64