In <Project>/node_modules/react-native/React/React.xcodeproj/project.pbxproj replace all occurances of 'port 8081' with '8088'. Redone every time you npm install or yarn add a dependency
Open project in xcode by File -> Open -> <Project>.xcodeproj. Then go to <Project>/AppDelegate.m and change jsCodeLocation to
jsCodeLocation = [NSURL URLWithString:@"http://127.0.0.1:8088/index.ios.bundle?platform=ios&dev=true"];
Run packager on port 8088 react-native start --port 8088.
Then run react-native run-ios.
Remove annoying Connection has no connected handler warning. react-native log-ios | grep -v nw_connection_get_connected