Thought I was hitting this same issue - turns out it wasn't quite the same as I did NOT have dconf-editor available.
Ended up figuring this out as follows:
virt-manager --debug
<...go into preferences screen...>
(virt-manager:10411): dconf-WARNING **: 03:20:30.256: failed to commit changes to dconf: Failed to execute child process “dbus-launch” (No such file or directory)
[Fri, 29 Nov 2019 03:20:30 virt-manager 10411] DEBUG (preferences:97) Showing preferences
Thought I was hitting this same issue - turns out it wasn't quite the same as I did NOT have dconf-editor available.
Ended up figuring this out as follows:
virt-manager --debug
<...go into preferences screen...>
(virt-manager: 10411): dconf-WARNING **: 03:20:30.256: failed to commit changes to dconf: Failed to execute child process “dbus-launch” (No such file or directory)
[Fri, 29 Nov 2019 03:20:30 virt-manager 10411] DEBUG (preferences:97) Showing preferences
apt install dbus-x11
all good now.