Plenty of streamers game on Linux you'll just rarely/never see it because it's all hidden behind the scenes and many keep their stream pretty clean from any technical stuff. Which is fine... but if you can't tell the difference from Windows then what's the point of even caring whether the streamer is using Linux or Windows or Mac or whatever else.

For Linux gaming content, I do like A1RM4X but he doesn't really stream live gameplay often if at all except to demonstrate certain features. He's mainly focused on showing off all different kinds of gaming tech in Linux, and it's very informative, he's got a thick accent though if that's a problem for you.