Based on Jim Angel's blog post and comment section.
This was ran against UniFi OS v3.2.9.
When moving from UniFi OS 1.x to 2.x, they switched their base OS distro to Debian, which removed the need for containerizing their applications. The original solution was to run wpa_supplicant from within a container on the host system's podman instance - however from 2.x this is no longer needed and the host system itself will run wpa_supplicant.
I did not realize this when I was updating, figuring it's about time to get on the latest version and having regular security patches again. These are the steps I followed after reading the comment section on Jim's original blog post.