Duct Tape?! Be sure to get a matching color!
Unfortunately, Apple uses a secret code for placing preferences on their iOS devices. Alphabetical is too easy, Categories are too complicated, separate prefs for each service too limiting.
I think they use a large Rubber-Maid tub holding all the prefs, they then stop strangers on the street and ask them to pull out a card. The order of those cards determines where the pref goes in one giant list. Pick a random number between 0 and 26 and sort the list by that letter. I think I heard that it's just a ploy by Apple to get us to let them do all the setup and to keep us out of
their OS!
I don't have an "8", but if you'll send me yours, I'll send you my "7" which does not flash when it rings.
If you insist on finding a setting for that, here are some suggestions:
Settings->Accessibility->Hearing/"LED Flash for Alerts" Check if that is "ON"
Settings->Notifications->Phone... nothing on mine about flashing the light
Settings->Phone... nothing on mine about flashing the light
DuckDuckGo?