https://arstechnica.com/information-technology/2019/02/atts-misleading-5g-e-indicator-comes-to-4g-iphones-in-ios-12-2-beta/

AT&T's misleading "5G E" network indicator for 4G phones, which was rolled out to some Android smartphones last month, has now come to iPhones in a beta version of iOS 12.2.