Steam Deck natively recognizes the PS3 controller. Simply plug it in via USB, wait for Steam OS to recognize it, then unplug USB cable and it will work over Bluetooth without needing
Amazon.com: Controller 2 Pack for PS3 Wireless Controller for Sony Playstation 3, Double Shock 3, Bluetooth, Rechargeable, Motion Sensor, 360° Analog Joysticks, Remote for PS3, 2 USB Charging Cords, Black : Video Games
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