Someone elsewhere in the thread linked https://www.openmotors.co/product/tabbyevo/, which I had never heard of before and which is actually pretty fascinating.

I'd obviously say the best open source vehicles are bikes and scooters, but I understand that currently isn't an option for everyone and that even in the ideal scenario there's going to need to be a small number of cars, trucks and vans. IDK how practical something like this will really be, but it's at least pretty neat.