How did this compare to the Carrington event?
The non-linear effect (20x weaker flare only 4x less effect) is accounted for by how Earth's magnetic field has weakened in the ~165 years since Carrington.
By the time you cannot use Internet, it’s too late—and it won’t be all over the news because guess how we make/broadcast/receive them. Worst case you won’t even get a radio transmission through.