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.
Source? Last I checked, the Steam Deck was very much in the minority even when narrowed down to just desktop Linux.
I confused it with Steam statistics sorry