I would assume the issue is all the variation in different distros. Plus the driver/hardware combinations. While some setups would just work they don’t see it as worth spending the time doing the validation/patching required. The steam deck is 1 device to test, with a single software stack. Much easier to target, and with a known customer base. Which brings up the other issue that they would be unlikely to make their money back on a general Linux release. Companies have cited this as a reason for not doing macOS releases in the past and based on the last steam survey Linux usage is in a similar ballpark (2.6% vs 1.8% for Mac ).

Despite all this I think it’s still a move in the right direction.