cloud-init-network.sh

user@server:~$ loud-localds -v --network-config=_master-net.cfg /tmp/seedmaster.iso user-data

user@server:~$ cat _master-net.cfg 
version: 2
ethernets:
  enp0s3:
    dhcp4: false
    dhcp6: false
    addresses:
      - 192.168.200.101/24 
    gateway4: 192.168.200.1
    nameservers:
      addresses: 
        - 4.2.2.4
        - 8.8.8.8
        
user@server:~$ sudo mount /tmp/seedmaster.iso /mnt/
mount: /mnt/: /tmp/seedmaster.iso is already mounted.

user@sh1-cmaster1:~$ cat /mnt/network-config 
version: 2
ethernets:
  enp0s3:
     dhcp4: false
     dhcp6: false
     addresses:
       - 192.168.200.101/24 
     gateway4: 192.168.200.1
     nameservers:
       addresses: 
         - 4.2.2.4
         - 8.8.8.8

cat /etc/cloud/cloud.cfg.d/subiquity-disable-cloudinit-networking.cfg 
network: {config: enabled}