If you honestly think that DF is Xbox biased, then you are probably too far lost to be helped at this point.
Digital Foundry regularly sings praises for the technical ability of Sony's 1st party studios, they particularly love Guerilla's Decima engine, praising it's capabilties in both their Horizon Zero Dawn and Death Stranding analysis videos. They praised the performance of multiplats on base PS4 for pretty much the whole generation, and recently have been highly critical of the poor performance of multiplats on base Xbox One (and rightly so, it has fallen to 720p-900p with less than 30 fps on many games the past year or two). Just recently they released a video singing praises about how good PS5's back compat is.
On the other hand, they also praise the technical ability of some of Microsoft's 1st party studios, particularly The Coalition's mastery of the Unreal Engine. They rightly point out the significant performance advantages of Xbox One X over PS4 Pro.
In other words, they are pretty balanced in their coverage, not really biased one way or the other. Rightly calling a console that is more powerful than another console, be it PS4 over Xbox One or Xbox One X over PS4 Pro, does not make them biased. Participating on the discord for a popular Xbox podcast does not make them biased.
You would think that with years and years of these comparisons and Xbone coming up short, it would have been Xbox fans convinced DF is biased but for some reason it is the other side of the coin.
I really think it’s that they aren’t negative enough towards Xbox for their tastes. It’s like that old yearbook quote meme where the guy says something along the lines of “it’s not just that I should succeed, others should fail” (yes I know it’s actually regurgitated from an old quote). They fail to realize that not everyone thinks in the console war mentality. Why would any professional outlet shit on either console, lol. They rely on them for games and hardware. They think DF should engage in talk about these things in the same way they themselves do on twitter and forums. I remember when GAF was in an uproar because DF didn’t do a video based on the video Sony made of the tear down. Give me a break.