The controller is un-bricked! All thanks to this user: https://redlib.catsarch.com/r/SteamController/comments/1tc3ua9/arrived_today_wont_connect_update_failed_bricked/

Symptoms:

• The firmware update failed.
• Turning on the controller causes the LED to flash red.
• The device takes charge from both the Puck and USB.
• Can’t connect wirelessly to the Puck.
• When connected using a USB cable, the device shows up as “Valve Software Steam Controller Bootloader” in lsusb’s output.

How to fix:

1. Start Steam in developer mode by using the -dev argument.

2. Open Settings -> Developer

3. Under Hardware Updates, press the Update all devices now button.

Steam will go through the usual firmware update steps and flashes all connected devices. This failed for me one more time, then worked fine once I switched to a proper USB C-to-C cable.

4. You might need to flash the Puck too, then pair it with the controller.

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Original post:

The controller worked fine until I started Steam. It showed the firmware update popup, I did as instructed, the puck was updated fine, but the controller failed. Now the LED flashes red when I turn it on, it doesn’t react to button inputs, doesn’t connect wirelessly, isn’t recognised as a controller when connected through USB, and shows up only as “Valve Software Steam Controller Bootloader”.

I think it’s reasonable to assume that the firmware is cooked. Naturally I’m opening a support ticket with Valve, but I’m wondering if anyone has any idea on how to resolve it without waiting, potentially for months, for a replacement.