I have used Android Auto in five vehicles now and will be installing it in my sixth car, an e93 M3, on March 6th.
Out of the four cars I own, I replaced the head unit in my e46 M3 with a new one. The other three Mercedes and one BMW have a Limcet box that connects to the existing head unit, allowing you to use either the stock system or access Android Auto wirelessly via the system display using an auxiliary connection.
There are likely more advanced systems than limcet, but that is the technology my fitter uses. I also have a reversing camera installed simultaneously if it is not already there.
Only one vehicle I purchased, the GLA 45, came with Android Auto pre-installed, but required the phone to be connected via USB. My 2018 C63S, equipped with smartphone integration, did not include Android Auto, which was unexpected. Had to get it via a third-party container.