With .NET 6 and CsWinRT, you can write your CreateDirect3DDeviceFromSharpDXDevice function like this:

private static IDirect3DDevice CreateDirect3DDeviceFromSharpDXDevice(SharpDX.Direct3D11.Device sharpDxDevice)
{
    if (CreateDirect3D11DeviceFromDXGIDevice(sharpDxDevice.NativePointer, out var punk) != 0)
        return null;

    return WinRT.MarshalInterface<IDirect3DDevice>.FromAbi(punk);
}