You can buy just a screen that is basically a tablet for CarPlay and android auto. It connects to your existing system via Bluetooth and to your phone via WiFi. Then it arranges the Bluetooth connection between your phone and the stock system.

https://www.amazon.com/s?k=CarPlay+screen&crid=6HTFE9CINT7K&sprefix=carplay+screen%2Caps%2C268&ref=nb_sb_noss_1

If my car lacked CarPlay, this is likely what I”d use, and mount it over or above the stock head unit.