how to enable tray icon on ubuntu 18.04 code example

Example: how to enable tray icon on ubuntu 18.04

install Ubuntu AppIndicators: sudo apt install gnome-shell-extension-appindicator

Restart gnome-shell: gnome-shell --replace &. This will restart gnome-shell from a terminal and run it in the background

You don't have to uninstall ubuntu - appindicator. Just turning on ubuntu - appindicator first in gnome-tweak, and then install topicon plus, there are no problems.