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 feel like both “people who install windows on the steam deck” and “people asking for advice for migrating to linux on reddit” are just vocal minorities which you encounter on the internet but don’t really influence the Statcounter’s results in a meaningful way. Generally (from my view) it’s the kids who got a steamdeck for xmass and the coders who use ubuntu for work influencing the numbers.