This doesn't give a complete answer, but according to Steam's Hardware and Software Survey, 31% of Steam's Linux users are using "SteamOS Holo". It's the name of SteamOS 3, used by Steam Decks. 2.57% of Steam users are using some Linux distro.

https://store.steampowered.com/hwsurvey/steam-hardware-software-survey-welcome-to-steam?platform=linux