Scribbles for my bad memory

This is because Debian 11/Debian 12 with Gnome does not ship with the packages to display tray icons. To install and enable the correct packages to display tray icons, run the following command:

sudo apt install gnome-shell-extension-appindicator

Then either reboot or log out and back in to Gnome, and run the following command:

gnome-extensions enable [email protected]

Reference