I tried on one gamepad, because I don't have more. I use old gamepad with direct input and I know this problem and know how to fix this :) Just need copy one emulator file :) Steam link is good, but I don't know how to connect, when game doesn't in steam
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For what it's worth, from within Steam, you can go to Games menu, then Add a Non-Steam Game to my Library. Put in the path to the executable, and presto, it shows up in Steam and can be called via Big Picture mode. This is how my kids and I have been able to play a few of the Epic Games Store giveaways from the family room TV.