Also while many individual stories might be in the center, bias is also exhibited in which stories they choose to print, or not to, as well as in esitorialized headlines.
This is part of why I like ground.news, they will show you blindspots based on the existence of reporting entirely. If you read mainly left or center news, the front page is about 50% stories that are mostly over covered by "right" news outlets (and vice versa).