Set up garage to open when car using Android Auto+phone arrives home?

With manual intervention: create an “Open the Garage” scene and add it to Android. Choose Android Auto in the app’s main menu, select Scene Notification, Arriving, Open the Garage. This should let you open it with one touch when you arrive home; none of my vehicles have Android Auto, and the version that runs on the phone screen is no longer available, so I haven’t used it in a couple of years and can’t confirm it still works.

You might be able to automate the confirmation for the option above via Tasker or similar.

With additional hardware: pick up one of these arrival sensors, set it up in your car, and create an automation that runs when this device, not your phone, arrives home.