There's already plenty of hardware components A) that non-domain experts would have no idea how to repair and B) with would it be potentially hazardous to meddl

There's already plenty of hardware components A) that non-domain experts would have no idea how to repair and B) with would it be potentially hazardous to meddle (e.g. a botched brake repair). I'm not really sure how software presents a substantially different risk. There's also a reasonable middle ground: vehicles will run unsigned code, but running software not signed by the manufacturer transfers all liability to the vehicle owner in case of bugs and/or malfunction. Third-party maintainers can provide signed builds and contractually agree to cover the same (allowing repair/maintenance even if the original manufacturer stops providing it).