If you search this forum for “TOCSS-DART” you will find:
https://discourse.gohugo.io/t/error-building-site-tocss-dart/48047/12
The Node.js Dart Sass implementation specifically excludes this capability, which is why this installation method is not listed in the Hugo documentation.
If I were you I would uninstall all instances of Dart Sass, cleanup my Brew cache, and install Dart Sass with Brew. Any problems you’re having with Brew are Brew problems, not Hugo or Dart Sass problems. The Brew installation method works great.