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.
I’m fairly sure it’s deficiencies in StatCounter’s measurement that’s accounting for it. Statistical noise, basically.
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.
And a portion of the “Windows” as well. Hiding in plain sight and all.
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.