Context: Last year I struggled for a long, long time to make my new Xbox Elite Series 2 gamepad work properly with Steam. After more than a day of frustration and following various trails of other discussions on the topic, I finally figured out the exact series of actions needed to solve the issue. I posted these steps on Reddit, and they ended up getting me dozens of comments and messages, even as recently as yesterday people still let me know that I saved them from the same frustration. With reddit in its current state of uncertainty, I'd hate for this guide to be lost, so I'm hoping new readers and controller fanatics will find it useful here.

The Problem: You have a Xbox Elite Series 2 Controller, which you are trying to use in Steam on Windows. When using the default (no profile lights) profile mode, the paddles are detected and can be mapped in Steam Controller config. However, they still register no input in-game when pressed. Here is how to fix your problem:

The Solution:

Step 1: You must first revert the firmware of the controller to version 4.8.1908.0. On a PC with your controller plugged in, open the Xbox Accessories app (from the Windows Store), then hit Windows + R to open the Run dialog. Run this command:

xboxaccessories:\firmwareupdate?legacyDowngrade=true

This should give you option to revert. Do it.

Step 2: In Steam Big Picture, go to Gear Icon -> Controller Settings and Enable Xbox Extended Feature Support if it isn't already checked. After enabling it you will have to Reboot. If it's already enabled, there is no need to reboot.

Step 3: Back to the desktop, make sure the Xbox Accessories app is CLOSED. If it is open, you must close it, then disconnect the controller entirely, then power it off, and then finally reconnect it to the computer.

Step 4: Press the central profile button on the controller a few times until it cycles through the profiles. You need to cycle it until the profile light turns off, indicating the controller is in its default layout.

Step 5: Open Steam's controller configuration for your game of choice, and you should now be able to re-map the paddles therein.

Every time I have done the above process, the paddles on the default profile (with no lights on) are now mappable in Steam and usable in-game. I have completed this successfully now with five total controllers, and all worked with Steam flawlessly afterward.

Notes & Clarifications:

• You do not have to uninstall the Xbox Accessories app. However, if ever you use it to modify the controller at all, you must repeat step 3. If you try to use the steam-remapped paddles in the game with the app open, they won't work. You have to turn off the app, disconnect and power cycle the controller, and then reconnect, and very specifically do not re-open the accessories app. I'm assuming this is because the Accessories app inserts some kind of override layer that only goes away after removing the controller and closing the app.
• This process will almost certainly make the Bluetooth connection wonky, if it even works at all. Instead, you'll want to use either a direct cable connection and/or the official wireless adapter. In fact, all of the above steps worked for me with the wireless adapter connection just as well as with the wired connection. As a bonus, you can seamlessly transition between wired and wireless mode this way by simply plugging or unplugging the cable.
• At least as of May 2023, I've received now multiple reports saying that newer purchases of the Elite 2 controller are being shipped with the controller now pre-flashed with a default firmware that is newer than the one that was available in the above post. As a result, this means that rolling back the firmware might not work, as it can't be rolled back to version 4.8.1908.0 anymore. However, I have since purchased two more new controllers of my own since then, and neither had this issue, and in fact both worked with Steam immediately out of the box (after telling Xbox app "no!" to firmware upgrades, that is).

I hope I have posted this correctly (it's my first post here!), and that others continue to find it useful.