According to Steam hardware survey https://store.steampowered.com/hwsurvey/?platform=linux 35% of Steam Linux users have "AMD AMD Custom GPU 0405" (the custom amd chip used by steamdeck). ~1 year ago it was 21%. That gives an upper bound of 35% from those 4% being Steamdeck. Although actual fraction is probably lower because:
* not every Linux user plays games or uses Steam, but probably almost all Steamdeck users use Steam.
* StatCounter numbers are based on website views. You can browse web on steamdeck but it's not very convenient, so I guess that, unless it's their only computing device and they have connected external monitor and mouse, most steamdeck users do most of their web browsing using their phone or computer instead of steamdeck.
* not every Linux user plays games or uses Steam, but probably almost all Steamdeck users use Steam.
* StatCounter numbers are based on website views. You can browse web on steamdeck but it's not very convenient, so I guess that, unless it's their only computing device and they have connected external monitor and mouse, most steamdeck users do most of their web browsing using their phone or computer instead of steamdeck.