Comment 51 for bug 1529079

Is the libvirtd.service named differently on the Ubuntu system? I'm pretty sure this is a systemd bug, where if the properties list After first and After names a non-existent unit the Before property will fail. If After names an existing unit or Before is listed first it works. From https://bugzilla.redhat.com/show_bug.cgi?id=1350909#c3

    # busctl call org.freedesktop.systemd1 /org/freedesktop/systemd1 \
        org.freedesktop.systemd1.Manager StartTransientUnit 'ssa(sv)a(sa(sv))' \
        test7.slice replace 2 After as 1 other.target Before as 1 fake.target 0
    Cannot set property Before, or unknown property.

    # busctl call org.freedesktop.systemd1 /org/freedesktop/systemd1 \
        org.freedesktop.systemd1.Manager StartTransientUnit 'ssa(sv)a(sa(sv))' \
        test7.slice replace 2 Before as 1 fake.target After as 1 other.target 0
    o "/org/freedesktop/systemd1/job/23660"

Whether or not the Before dependency exists never matters.