what? or just transfer from PC to PC via wifi through steam negating any SD card..
https://help.steampowered.com/en/faqs/view/46BD-6BA8-B012-CE43
use PC 1 that already has it downloaded and installed, and have pc2 download from PC 1.. why worry about a 3rd hard drive or rehoming the SD card and potentially screwing the file structure up by potentially inserting Linux (steam deck) into what I can only assume would be a Windows based pc