Keep announcing devices with the window closed

When a device that is not authorized is plugged in, USBGuardGUI announces it — as a toast if the window is in front, otherwise as a desktop notification with an Allow for this session button. The button re-checks that the device is still the one announced before acting, since USBGuard reuses device numbers.

To keep announcing after the window is closed: Main menu → Preferences, and turn on:

• Keep running in the background — closing the window hides it instead of quitting;
• Start at login — start hidden when you log in, so the first device of the session is announced too. Not offered in the Flatpak.

With and without a status icon

Where the desktop provides a status icon area (KDE Plasma, Xfce, Cinnamon, and others), an icon appears while the program runs in the background: click it to reopen the window, or use its menu to quit.

Stock GNOME has no status icon area — it needs the AppIndicator and KStatusNotifierItem Support extension. Without it, the program still runs and still announces devices; the first time you close the window it tells you so. To reopen the window, launch USBGuardGUI again from the application menu; to quit, use Main menu → Quit (or Ctrl+Q).