Got in an iPhone 8, wouldn’t charge. Also wasn’t seen by a computer in itunes. Also wouldn’t boot when power was plugged into USB. Very similar symptoms to a “Tristar” failure in earlier phones, but the 8 doesn’t have a Tristar. It has a new chip called “Hydra”. Replaced Hydra only to discover it didn’t fix the issue.
Studying the schematics I realized that the data communication from a computer doesn’t go to Hydra anymore, instead it goes to the chip that actually provides the charging energy to the battery, called “Tigris”.
Replaced Tigris, all problems solved.