Linux holds a market share of approximately 14% in India.
I'm not sure how accurate StatCounter is, given that most Linux users use adblockers. However, according to it, Linux has almost a 14% desktop share in India.
That's because even a grey market Windows key costs US$20 nowadays and that's over ₹1,600. For comparison purposes, the largest Indian banknote is ₹500.
It's a little puzzling to me that Linux isn't popular in low-income countries. Why wouldn't it be the OS of choice there? Do we need to become linux missionaries? I imagine it would be easier to convince people who can't buy an iPhone to use FLOSS than those who can drive to an Apple Store and waddle over to get yet another one.
I'm not sure adblockers change the OS they report. Other tools I know for a fact do it.
Edit: However, as @aebletrae@hexbear.net mentions, adblockers don't have to change what OS is reported to change the overall statistics. They explain how in a comment below.