I noticed this when it was first announced on HN as well. Hoping to give it a try as well shortly.
network:
version: 2
renderer: networkd
wifis:
wlan0:
regulatory-domain: "AU"
dhcp4: true
dhcp6: false
optional: false
access-points:
"<access-point-name>":
password: "<password>"
The important parts are: bootcmd:
- sysctl net.ipv6.conf.all.disable_ipv6=1
The rest of the configuration is standard, though I purposefully made the wi-fi non-optional so I could confirm that wi-fi worked (my only Internet at the moment is through my iPhone hotspot, which was another source of issues, but that's a whole other story).