It's not like consumer electronics contain top secret tech like EUV machines. All supply chain for firmware / software of 99.99% devices is very boring, contains absolutely nothing secret and the only reason why it's "difficult" is because IP owners was not bothered.
Once single EU / US legislation introduced that force manufacturers into opening end-of-life products all IP right owners will either immediately make it possible or go out of business.
Since everyone will be forced to do the same no one will gain any advantages.