For Porsches, it's easier as they do share infotainment stuff with other VAG vehicles and there is an online community that also tinkers with PCMs (Porsche's infotainment).
In my old 991.2 I managed to unlock Android Auto which was never officially supported using that community's efforts - it was completely functional, just disabled in favor of a CarPlay-only offering. (This changed with the 992 where it comes with both systems standard). And by plugging in a Motorola MA1 one has Wireless Android Auto on a car that never supported even the wired version. Sweet.
One day we might see a real Doom on 911 write up because the viral video from a few years ago is sadly fake. But just by going with the information/tools available in the modding community it's completely possible. Most of the GUI on it is Java apps BTW :)
I find wireless Carplay, especially when using Google Maps, drains the battery like crazy. I always plug it in anyways to charge for any ride longer than 10 minutes.
That said, cars have 12v batteries. If the pi was better (again another gripe, choose better products not just what everyone else uses) you could put the thing to sleep. Even a good low power Linux machine can go years off one of those (quick math says like 100 years, so negligible draw). Or you could cut yourself off if the level gets below a threshold for too long. Plenty of solutions.
I have reverse camera connected to SBC with Allwinner H6. It easily saves around 5 seconds compared to Pi (their closed bootloader takes ages to even start loading kernel). I considered early booting the system when opening the door, but really it is fast enough already.
