• The way I read the article, it does not give a precise answer, but it provides a strong hint in two different paragraph:

    NewsGuard, which rates the quality and trustworthiness of news sites, has identified 1,197 pink slime sites operating in the US as of April 1…
    […]
    Of the pink slime outlets identified by researchers, the largest is the conservative-leaning Metric Media, which consists of about 1,000 local titles, according to the website for its parent company.

    So yeah, if the researchers identified some ~1200 sites and one right-wing news network claims to operate 1000 all on its own, then there has to be a very obvious dominance of right-wing “pink slime” news outlets.