Your able to add native linux games such as supertux which will be categorised as linux games
Your able to add windows games which use wine which be categorised as window games
Your able to add steam games which runs steam URLs which be categorised as linux games
But what if you use steamplay/proton? When You add a game using the steam runner it will be categorised as a linux game even though the game is a windows game.
Please allow us to choose the platform in the runner settings manually.
Same goes for emulators such as ePSXe, Dolphin, PCSX2 and DeSmuME which I prefer over retroarch. I can add them using the linux runner but they will be categorised as linux games even through they are console games.