chuckled a little when reading the first negative of luna was the absence of having a debian 10 template. i raised a ticket with them about this in july, and have been periodically testing new openstack releases from https://cdimage.debian.org/cdimage/openstack/current-10/ to see if the issue 'fixed itself' for some reason with debian 10, cloud-init takes around 6 min to raise network interfaces, which is why they haven't released a template yet. not sure if the issue is on lunas side or not.