There is an alternative way to open your garage door from your Audi e-tron GT without using Homelink, called Apple Carplay. Your Audi e-tron GT is certified by Apple to use Carplay.
CarPlay is a piece of software that allows your Apple iPhone to interface with your Audi e-tron GT's built-in entertainment and information system. CarPlay increases convenience and reduces distraction by putting commonly used apps, that would be necessary or especially useful while driving on your car's infotainment display. By doing so, CarPlay minimizes the need to actually handle your iPhone while driving.