Failed to transform "ananke/css/main.css" (text/css)

I’m trying to start with hugo, and it seems cool. However, when I try to run hugo server -D (as per the the quick start guide), it fails, giving me this:

Start building sites … 
hugo v0.86.0-41C6C52E linux/amd64 BuildDate=2021-07-21T09:53:14Z VendorInfo=gohugoio
Error: Error building site: TOCSS: failed to transform "ananke/css/main.css" (text/css). Check your Hugo installation; you need the extended version to build SCSS/SASS.
Built in 30 ms

I know that I need the extended version to build .scss and .sass files, but the file is text/css.

Here’s my OS info:

Node / npm:

$ node --version
v16.2.0
$ npm --version
7.19.0
$ postcss --version
8.3.1

Hugo:

hugo v0.86.0-41C6C52E linux/amd64 BuildDate=2021-07-21T09:53:14Z VendorInfo=gohugoio

It was installed by a .tar.gz file from the GitHub releases page.

Install the extended version.

Could you tell me how to do it ?

@gd1214b See documentation.