The Steam Deck compatibility notes for the game specifically say that it isn’t good at handling multiple controllers:
This game does not default to external Bluetooth/USB controllers on Deck, and may require manually switching the active controller via the Quick Access Menu
I think it is likely that this problem comes from the game, not a problem with streaming sending the inputs. You can try testing this in another game with more flexible controller support to narrow it down.
The Steam Deck compatibility notes for the game specifically say that it isn’t good at handling multiple controllers:
I think it is likely that this problem comes from the game, not a problem with streaming sending the inputs. You can try testing this in another game with more flexible controller support to narrow it down.