https://www.techradar.com/news/if-your-iphone-8-logic-board-breaks-apple-will-replace-it-for-free

Got an iPhone 8 with a faulty logic board? Breathe easy, because Apple is going to fix up your phone for free – it says a "very small percentage" of handsets have developed problems, and has opened up an official replacement program to get them all fixed.

Eligible devices would have been bought between September 2017 and March 2018, Apple says – that's the first six months that the phone was on sale after launch. The issue apparently doesn't effect the other handsets Apple unveiled in September 2017, namely the iPhone 8 Plus and the iPhone X.