boot rpi
write network: {config: disabled} to /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg
write the following to /etc/netplan/01-netcfg.yaml:
network:
  version: 2
  renderer: networkd
  wifis:
    wlan0:
      dhcp4: true
      dhcp6: true
      optional: true
      access-points: 
        "******":
          password: "**********"
then do:
sudo netplan generate
sudo netplan apply
reboot