By skyforbes And (b) with ChatGPT there is of course no way to launch it handsfree (and probably never will be on an Android system). So you have to open the app with touch navigation, then press the voice mode button. There used to a be a single 1×1 voice mode shortcut widget. They stupidly got rid of it earlier this year and now there's just a huge 3×2 widget that had a prompt box and multiple buttons.
Even if you could say, "Hey ChatGPT" you can't tell ChatGPT to control your smart home devices like you can with Gemini. At least not with maybe some convoluted workaround. Gemini just works since I have a Nest Hub.
Is as if a lot of these developers don't have a life beyond their computer screen and really try to use their own apps in a variety of everyday practical scenarios.