Steam decks have been out for years now, and even though they sold millions of copies they're not the majority of Linux machines, you can check the GPU AMD Custom GPU 0405 on the GPU field since that's the steam deck one, it's at 0.82% and had a 0.23% increase this month. So some of the increase in Linux came from it (around half), but there's still a lot of new Linux PC users.
Also it's worth mentioning that every time that the Linux share has gone down it coincides with a spike in Chinese language usage.