With apologies for gently calling bullshit on this, you're basically saying the following list does not exist. Or you're saying it has "center bias," which is kind of like saying a court has "bias towards its decision". Or you're saying this domain is biased, even though it seems balanced (I've looked into it), an accusation that would of course require evidence:

https://mediabiasfactcheck.com/center/

There is an objective truth. The closest you come to that, the less biased you are. Not sure what the problem with understanding this is. Values may differ, and you may be including that in your definition of "bias" (for example, WSJ may come at news from a business perspective), but I would personally NOT include values into a definition of "bias" because that then makes "bias" conveniently impossible to define objectively!