My Ionic info:
cli packages: (/usr/lib/node_modules) @ionic/cli-utils : 1.9.2 ionic (Ionic CLI) : 3.9.2 global packages: Cordova CLI : 7.0.1 local pack
Please use these commands in your project.
sudo sysctl fs.inotify.max_user_watches=524288 sudo sysctl -p --system
And again run ionic serve