Saw a mention of this in an earlier post so I Googled and found this article that explains the procedure. I went looking as I tried it by just starting the AA app but it was limited. I haven't had time to use the procedure and won't for a day or two so let me know if it works.
www.autoevolution.com

How to Get Started with Android Auto Wireless After Updating to Android 11
The Android 11 rollout has officially started, and for Android Auto users, the biggest change concerns the wireless mode, which is now available for all devices running the new OS version.