There is an alternative way to open your garage door from your Audi Q8 without using Homelink, called Apple Carplay. Your Audi Q8 is certified by Apple to use Carplay.
CarPlay is a piece of software that allows your Apple iPhone to interface with your Audi Q8'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.