The large nuclear bomb they just blew up was about 1.6 Megaton, most certainly an enhanced two-stage bomb (a hydrogen bomb, though probably not “portable” but built and assembled in the dug-out tunnel they bored underground.
Because it was an underground nuclear blast, there was no above-ground pulse released high above ground that creates the EMP damage we discussing.
But, because it was a successful “test” of a hydrogen bomb, it brings North Korea much, much closer to being able to build a bomb that CAN be lifted into the atmosphere to create a wide-area EMP pulse that CAN damage many electronics.
Now NK has a direct threat to the US, not just Japan or SK.