Google might soon have an alternative to voice matching when you want to use Assistant to get personalized results. The latest beta for Android's Google app includes code references to a previously hinted-at Face Match feature that, as the name implies, would scan your visage to provide tailored commands on camera-equipped devices. While there isn't a detailed description, you'd have to both train the system and could add multiple devices. Your face profile wouldn't be limited to one gadget, which some companies do in the name of security.
You could also invite other people to create profiles.
There's no clue as to when Face Match might launch, assuming it launches in the first place. The absence of imagery and other content implies that it might not arrive for a while. It could make sense, though. So long as your device has a camera (no Home Hub users need apply), you could view sensitive info or issue commands without having to create a voice profile. This might also be an accessibility feature -- people who can't speak could still get a customized, private experience in a multi-user household.