Without knowing the methodology that StatCounter is using, the numbers themselves aren't especially meaningful, although a consistent upward trend in those numbers could be showing something real.
In any case, ChromeOS is also Linux, so tack that on there as well, along with whatever portion of that 7% "unknown" that you think is reasonable (which could be a relatively large portion, depending on methodology).
(Also, the bar chart shown in the article is messed up because they're charting the value of each item averaged over the previous year.)
For numbers I did like to see absolute numbers. While I have no doubt that people are switching to Linux, but an increasing number of people are also just giving up on computers in favour of just using their phones for everything. Some of the increase in percentage Linux is seeing could also be due to Windows and Mac users dropping having a computer in general.
That's not to say that people aren't switching, I see no reason to get a new Mac next time I'm replacing my laptop. My work will be done more easily on Linux at this point.
It could also be showing that the market is consolidating towards big tech and that only those wanting to stay with their independent statistics provider are still with StatCounter. In turn, the users of services with such morals could be more likely to be Linux distribution users.
I don't have data better than StatCounter, but if we're thinking of methodology and whether it could be accurate, this is a possibility to take into account
The optimist in me wants to not leave unmentioned that Linux is more accessible than ever and information easier to come by while Windows has never been shittier (which old Windows version shipped with tracking and ads?) and macOS is still priced and protected the way it always has been: much easier to dual or live boot Mint. Come for the freedom and stay for the ease of use. It's no coincidence that Microsoft made it very easy to use Linux software within Windows now (obviously without contributing the inverse mechanism, that'd be stupid): people want it. I really hope there's more truth to this than to the first paragraph
ChromeOS uses the Linux kernel in a browser based userspace, and offers a VM for running GNU/Linux as guest OSes, isn't quite the same as being GNU/Linux, otherwise Windows with WSL is also Linux.
In any case, ChromeOS is also Linux, so tack that on there as well, along with whatever portion of that 7% "unknown" that you think is reasonable (which could be a relatively large portion, depending on methodology).
(Also, the bar chart shown in the article is messed up because they're charting the value of each item averaged over the previous year.)