DuckDNS docs: json instead of YAML

The doc page for DuckDNS configuration shows how to configure the service:

  "lets_encrypt": {
    "accept_terms": true,
    "certfile": "fullchain.pem",
    "keyfile": "privkey.pem"
  "token": "sdfj-2131023-dslfjsd-12321",
  "domains": [""]

but this is a json syntax, not YAML. So, where I need to put this code?

It goes in the add-on config.

It doesn’t go in your Home Assistant configuration.

Are you using hassio or home assistant installed another way? If you are running hassio did you install the duckdns add-on?

Ah ok, it wasn’t very clear to me.
I installed HA using Python in VirtualEnv on a Debian - no

This is the official documentation for your install method,

This one is easier to implement IMO

If you are looking at something for Home Assistant and the page is under /addons/ it is referring to hassio addons which are not available on any other platform at this time, other than hassio.