Interrupt 0 (INT0) on the ATmega chip is not the same as what the Arduino libraries define as Interrupt 0.
This is how the Mega boards have always worked, so I'm confused on what you think changed.
Interrupt 0 (INT0) on the ATmega chip is not the same as what the Arduino libraries define as Interrupt 0.
This is how the Mega boards have always worked, so I'm confused on what you think changed.