I just got Android Auto working the way I wanted it without root. I had the same issue of the car simply not seeing my phone at all.
This worked for me for an after market unlicensed android auto unit. You can get these Chinese aftermarket radios (they come under different brandnames like Maxtron or Cartronix) that comes with a canbus converter, in my case a Saab 9-3 from 2009. The nice thing is they have a front that looks like the stock unit and is super easy to mount in the original mounting. Parking sensors, steering wheel control, everything works. The only thing is, because this is an unlicensed android auto you need an app that is installed on the head unit called Tlink5 to help connect. I think this is why (in my case) android auto would not work. It needs to have developer options and unknown sources activated in android auto on your phone to work.
First off, what I didn’t get at first is this:
e/os comes with an android auto stub not the app, there is no way to set the right permissions (like developer mode and unknown sources) in the stub settings. You can also not uninstall it on your phone (at least I haven’t found a way). And the Applounge thought that android auto was installed already.
So activate developer mode on your phone (in settings > about phone > tap the build number 10 times. Next go to settings > system > developer option and set USB debugging).
restart phone.
Next connect the phone to a pc and use adb commands to remove the android auto stub from your phone (see for instance https://xdaforums.com/t/uninstall-bloatwares-no-root.4321387/) the package you want to uninstall is: com.google.android.projection.gearhead
To be safe restart phone
Install the needed stubs for google maps, google app and speech thing (see How to run Android Auto without Google apps ) Or use the original google apps if you prefer (but who would?).
To be safe restart phone
Open the Applounge you can now install the actual android auto app through the store. Next go to settings > apps > Android Auto Stubs (for some reason it’s still called a stub). Next tap Additional settings (this is the option that is missing from the original stub) and scroll to bottom, hit the build number 10 times to allow developer options, next tap the 3 dots in upper right corner > Developer settings > allow unknown sources.
Now connect to the car (in my case it works wireless and with cable)
Don’t forget to set the needed permissions for notifications etc (the car prompted me for this)
I now have Android Auto working with no other google dependencies and I can use Mapy for navigation.