Ubuntu16: NOK ( nothing works )
I cannot confirm this. Cloud-init works fine in images:ubuntu/xenial/cloud.
OpenSuSE 13.1: NOK ( nothing works )
I presume you mean 15.1 since we don’t have an openSUSE 13.1 image. Again, I cannot confirm this using images:opensuse/15.1/cloud.
CentOS 6: NOK ( cloud-init is not installed )
[root@centos-6-cloud ~]# rpm -qa | grep cloud-init
cloud-init-0.7.5-10.el6.centos.2.x86_64
Could you possibly paste the config(s) you are trying to use and are failing?