It peaked at 4.05% in March. The last 2 months it went just below 4% as the Unknown category increased. For June the reverse happened, so 4.04% seems to be the real current share of Linux on Desktop as desktop clients were read properly/werent spoofed.
It’s probably even higher than that. These stats are mostly based on website visits I believe. And many Linux users are also privacy-minded and might spoof their OS in the browser. I bet a large portion of the Unknown is actually Linux too.
It’s hard to tell, as there are so many things that influence it. A huge factor is selection bias, as only a small number of website embed StatCounter, and that’s very likely to not be a representative sample. I’d bet that the influence of that is magnitudes larger than of user agent spoofing.
And a portion of the “Windows” as well. Hiding in plain sight and all.