> Is there a definitive story that someone actually did hack these units on a grand scale?

Given the scope here (see map at https://en.wikipedia.org/wiki/2026_French_supermarket_refrig...), it'd either be individual hackers getting inspired from their neighbor hackers, or one actor targeting European countries.

Although seemingly the hack wasn't so sophisticated, maybe it's truly just some kids fucking around with what they see being open, and maybe just want to target European countries for the "lulz" or whatever, who knows.