fcitx on debian 11/debian 12 missing tray icon solution:
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 ubuntu-appindicators@ubuntu.com