WebXR Legacy Input

I have my Input Manager configured with TriggerLeft + TriggerRight using Joystick Axis 9/10 as defined at both:

https://docs.unity3d.com/Manual/xr_input.html
and
https://github.com/MozillaReality/unity-webxr-export/blob/master/ProjectSettings/InputManager.asset



In my project, this never fires in WebXR:

Code (CSharp):

1. void Update () {
2.         bool isSpace = Input.GetKey (KeyCode.Space);
3.         bool isTrigger = Input.GetAxis ("TriggerLeft") > 0.8f || Input.GetAxis ("TriggerRight") > 0.8f;
4.  
5.         if (isSpace || isTrigger) {
6.             // Do work
7.         }
8. }

I've also tried attaching a WebXR Controller script and listening for events with:

Code (CSharp):

1. WebXRController controller;
2.  
3. void Awake () {
4.     controller = GetComponent<WebXRController> ();
5. }
6.  
7. void Update () {
8.     if (controller != null) {
9.         if (controller.GetButtonDown ("Trigger")) {
10.             /* Do work */
11.         }
12.     }
13. }

But this still fails to capture Oculus Quest controller input when viewing this content from the Oculus Browser in the WebXR environment.

What am I missing to connect these controller inputs to the loop?