It is absolutely not a reliable source. It’s an amateur operation run by one guy (who describes himself as “an arm chair researcher on media bias”) as a side-gig.[33] The methodology is utter pants[34], and the website changes ratings if users complain or on the basis of user ratings. The methodology is basically nothing more than unknown people clicking a few articles on a website, and then determining bias. How it got mentioned by BBC News and slipped past the fact-checkers, I do not know (that Newsweek covered this site makes more sense given that Newsweek has been awful for years). To what extent it’s been cited by those computer scientists (note that this is not in peer-reviewed research), it’s been as a collection of fake news websites (i.e. not for its determination of media bias in non-fake news websites). The website is such an amateur operation that it can’t even do a proper reference list consistent with any style guide, see the bottom of this link[35]. Every time it’s mentioned on the RS noticeboard as a determinant of RS status, an angel dies.