Legion Go S: Trackpad not detected and physical controls stop working in Desktop Mode on SteamOS 3.8.16

Your system information

• Steam client version: 1788291500 / SteamClient023
• SteamOS version: 3.8.16
• Device: Lenovo Legion Go S (SteamOS)
• Opted into Steam client beta?: No
• Opted into SteamOS beta?: No
• Have you checked for updates in Settings > System?: Yes

Please describe your issue in as much detail as possible:

Since updating/running SteamOS 3.8.16 on my Lenovo Legion Go S, I am experiencing two input-related issues.

1. Trackpad input is no longer detected

The Legion Go S trackpad does not appear to register any input in SteamOS.

I verified this using:

Settings > Controller > Legion Go S Controller > Details > Begin Test

During the controller input test, touching or moving a finger across the trackpad produces no detected input.

Expected behavior:
The trackpad should register input and appear responsive during the controller input test.

Actual behavior:
The trackpad does not register any input.

2. Physical controls do not work in Desktop Mode

After switching from Gaming Mode to Desktop Mode, nearly all physical controls on the Legion Go S stop responding.

The touchscreen continues to work normally. The top-left Legion Go S button that opens Steam also continues to function, but the other physical controls, including the sticks, directional controls, buttons, and trackpad, do not appear to provide input.

Expected behavior:
The Legion Go S physical controls should continue to function in Desktop Mode, including the controls used for mouse and navigation input.

Actual behavior:
The touchscreen works, but nearly all physical controls stop responding. The only physical button I have found that still works is the top-left button used to open Steam.

Both issues are reproducible after restarting the device.

Steps for reproducing this issue:

Trackpad issue:

1. Start the Lenovo Legion Go S running SteamOS 3.8.16.
2. Open Settings > Controller.
3. Open the details page for the Legion Go S Controller.
4. Select Begin Test.
5. Use the trackpad.
6. Observe that no trackpad input is detected.

Desktop Mode input issue:

1. Start the Lenovo Legion Go S in Gaming Mode.
2. Select Switch to Desktop.
3. Wait for KDE Desktop Mode to load.
4. Attempt to use the physical controls, including the sticks, buttons, directional controls, and trackpad.
5. Observe that the physical controls do not respond.
6. Use the touchscreen and observe that touchscreen input continues to work.
7. Press the top-left Steam button and observe that it still opens Steam.

Start by reproducing both failures on a Lenovo Legion Go S running SteamOS 3.8.16: test the trackpad under Settings > Controller > Legion Go S Controller > Details > Begin Test, then switch from Gaming Mode to Desktop Mode. Trace the controller behavior across the mode change; done means trackpad input is detected and the physical controls work in Desktop Mode while touchscreen behavior remains intact.