Comment 2 for bug 1808044

Hi and thanks for your report,
this does not have the complete logs, so I might struggle to see the root cause, lets try.

The interesting lines I see int he bug are:
E: Command line option --mode is not understood in combination with the other options
 dpkg: error processing package libvirt-daemon-system (--configure):
  installed libvirt-daemon-system package post-installation script subprocess returned error exit status 100

That is not an error I have seen before.
The failing script is /var/lib/dpkg/info/libvirt-daemon-system.postinst

The only "--mode" I see in there is on:
  install --mode 644 /dev/null "$LOCAL_APP_PROFILE"
Which is added by dh_apparmor (adding apparmor bug task for that).

One such section looks like:
304 LOCAL_APP_PROFILE="/etc/apparmor.d/local/usr.lib.libvirt.virt-aa-helper"
305
306 test -e "$LOCAL_APP_PROFILE" || {
307 mkdir -p `dirname "$LOCAL_APP_PROFILE"`
308 install --mode 644 /dev/null "$LOCAL_APP_PROFILE"
309 }

There is no conditional in between, so this will always be:
 $ install --mode 644 /dev/null "/etc/apparmor.d/local/usr.lib.libvirt.virt-aa-helper"
I don't see where that would fail.

Maybe the apparmor developers know a bit more about this, for libvirt I'd not know where to continue on this.