Webgpu on firefox

I am on the latest firefox for linux: 115.0.2 (64-bit) (NOTE: Same issue on Firefox 116.0b5 (64-bit))

I enabled webgpu using about:config like so:

Yet, when running an example, the browser reports no support:

Why doesn't firefox let me run webgpu code?

$ inxi -G
Graphics:
  Device-1: Intel AlderLake-S GT1 driver: i915 v: kernel
  Device-2: AMD Ellesmere [Radeon RX 470/480/570/570X/580/580X/590]
    driver: amdgpu v: kernel
  Display: x11 server: X.Org v: 1.21.1.7 with: Xwayland v: 22.1.8 driver: X:
    loaded: amdgpu,modesetting unloaded: fbdev,radeon,vesa dri: iris gpu: i915
    resolution: 3840x2160~60Hz
  API: OpenGL v: 4.6 Mesa 23.0.2 renderer: Mesa Intel UHD Graphics 770
    (ADL-S GT1)

Vulkan information:

Devices:
========
GPU0:
    apiVersion         = 1.3.238
    driverVersion      = 23.0.2
    vendorID           = 0x8086
    deviceID           = 0x4680
    deviceType         = PHYSICAL_DEVICE_TYPE_INTEGRATED_GPU
    deviceName         = Intel(R) UHD Graphics 770 (ADL-S GT1)
    driverID           = DRIVER_ID_INTEL_OPEN_SOURCE_MESA
    driverName         = Intel open-source Mesa driver
    driverInfo         = Mesa 23.0.2
    conformanceVersion = 1.3.0.0
    deviceUUID         = fd8cf190-0bdb-4dd5-b941-a7eb5b383e9c
    driverUUID         = 9bb8225e-db2e-6a20-282d-526794955fa9
GPU1:
    apiVersion         = 1.3.238
    driverVersion      = 23.0.2
    vendorID           = 0x1002
    deviceID           = 0x67df
    deviceType         = PHYSICAL_DEVICE_TYPE_DISCRETE_GPU
    deviceName         = AMD Radeon RX 580 Series (RADV POLARIS10)
    driverID           = DRIVER_ID_MESA_RADV
    driverName         = radv
    driverInfo         = Mesa 23.0.2
    conformanceVersion = 1.2.7.1
    deviceUUID         = 00000000-0100-0000-0000-000000000000
    driverUUID         = 414d442d-4d45-5341-2d44-525600000000
GPU2:
    apiVersion         = 1.3.238
    driverVersion      = 0.0.1
    vendorID           = 0x10005
    deviceID           = 0x0000
    deviceType         = PHYSICAL_DEVICE_TYPE_CPU
    deviceName         = llvmpipe (LLVM 15.0.7, 256 bits)
    driverID           = DRIVER_ID_MESA_LLVMPIPE
    driverName         = llvmpipe
    driverInfo         = Mesa 23.0.2 (LLVM 15.0.7)
    conformanceVersion = 1.3.1.1
    deviceUUID         = 6d657361-3233-2e30-2e32-000000000000
    driverUUID         = 6c6c766d-7069-7065-5555-494400000000

Update

Same issue on chromium:

And chromium even states that it has WEBGPU enabled:

I'm not sure what could be the problem with Chrome, because in Chrome 113+ WebGPU is enabled by default and it works for me. Maybe some sort of Linux/driver-specific problem? However, the problem with Firefox is exactly what the error message says:

WebGPU is not yet available in Release or Beta builds.

You have to use the Nightly build. Note, that even in the Nightly build WebGPU is not fully supported.