There seems to be a small community of DIY vehicle builders, but they tend to stick to forums and such. I think because of liability issues (and rules for cars are pretty strict as they are), there isn't a lot of sharing between builders beyond the basic frame
I don't know how reliable things like CANpie or Can4linux are (Controller Area Network or CAN used for internal systems communication in vehicles, and these are open source)
The social network of the future: No ads, no corporate surveillance, ethical design, and decentralization! Own your data with Mastodon!