Unfortunately that straightforward solution might also compromise other aspects of the vehicle and/or might also be illegal if it disables a mandatory safety system.

The "straightforward" solution is to tell vehicle manufacturers that they aren't allowed to sell vehicles with connectivity unless they also have proper security and privacy protections in place. If no-one can give them money for it then they won't do it.

That's a workaround, not a solution. And a partial one at that since it only affects your own vehicle; you'll still be in danger from other people's connected vehicles.