not that difficult
never mind fancy onscreen reset menus or glovebox buttons, just ask the question when you connect a new phone, new owner or additional driver.
as for older cars and simplicity, then anything pre ~2002 with only the most basic on board computers. or, better still, something with a carburetter, no sensors to break, no catalytic converter to fail and no computers or ECU. Yes, things can and do still fail, but you don't need an electronics degree to fix, just a spanner and a screwdriver