The number doubled in the last year. April 2025 it was around 2.3%, and has been jumping around 2-3% for several years. Skyrocking seems justified when looking at a greater picture.

Though, it's a longer process, not something that suddenly happened immediately. The combination of Steamdeck, proton, good gaming-distributions and Windows 10 phasing out, while Windows 11 sucks and becoming an AI+Ads-infested mess, seems to have pushed this trend. So let's see how high this sky will be.

Edit: Found a good visualization: https://www.gamingonlinux.com/steam-tracker/