As you may have guessed from the title, this blog is currently deployed on netlify. As they claim in order to integrate a given theme one should add it as a submodule:

cd YOUR_PROJECT_DIRECTORY
git init
git submodule add https://github.com/THEME_CREATOR/THEME_NAME

Well, this didn’t work for me. What did work was explicit addition of the release, like this

git submodule add -f https://github.com/dsrkafuu/hugo-theme-fuji.git@v2.8.2-migurdia themes/fuji

In my case v2.8.2-migurdia is the latest tagged version of the theme. After this minor touch and following the documentation I got what I wanted.