Yes, it only works with the voice remote. The microphone icon won't show up if you are not using the voice remote.
Just confirming, are you sure the microphone icon only appears if we're using a Voice Remote?
I am asking because I saw this in the documentation:
"When customers sign up for a channel or sign in, they can use their Roku voice remote or mobile app to audibly enter their credentials on a voice-enabled keyboard."
Also, when I ran the sample channel, I realized that even when voiceEnabled=true, it becames false. I don't know why, but it makes me think I'm doing something wrong.
m.keyboard = m.top.findNode("theKeyboard")
m.keyboard.domain = "email"
m.keyboard.textEditBox.voiceEnabled = true