There was another NLP study done three months ago, which this study is based on. That study focused on three other major US newspapers and their bias. Those three were:
The New York Times (seemingly the biggest offender)
The Washington Post
The Wall Street Journal
It would be great to have some kind of unified framework that could ingest the link to a news site and use NLP to fully analyze their language, though I suspect that it’s difficult to fully automate, as the existing studies needed to do some data cleaning by hand.