OK this does involve some physical dash work but for older cars with either very basic or no head units, this could be worth thinking about. I must say I'm really impressed with all the functionality and integration with ODB2 sensors, Apple CarPlay, and Android Auto. The problem with newer cars is there is often a lot of car functionality built into the head unit, e.g. climate control, etc.
Building a Raspberry Pi 4 In-Dash Car Computer w/ Android Auto (Raspberry Car Stereo)
by DB Tech on YouTube