Do you mean to say when you edit the network config box, and fill it out with your own network info (adhering to this standard: that cloudinit in the vm gives a yaml error? This indicates the way you filled out the entry box is not properly formatted. Keep in mind to pass networking info, your cloudinit install in your template VM needs to be set to use nocloud data sources, and keep in mind the network configuration passed via cloud-init is added to the template VM, not replaced, so you need to properly configure your template VM to not already have adapters configured with IP addresses etc