Your system information

• Steam client version (build number or date): 1778003620 (stable)
• Distribution (e.g. Ubuntu): NixOS 26.05
• Opted into Steam client beta?: No
• Have you checked for system updates?: Yes
• GPU: NVIDIA GeForce RTX 3090 + NVIDIA GeForce GTX 1660 SUPER

Please describe your issue in as much detail as possible:

Left-clicking the Steam system tray icon does nothing. The Steam main window should be restored/focused.
Right-click on the same icon works correctly — the context menu appears and the "Open" menu item can be used to restore the window.

The tray icon itself appears correctly (Steam uses the org.kde.StatusNotifierItem D-Bus interface). A StatusNotifierWatcher is present on the session D-Bus (org.kde.StatusNotifierWatcher is registered). The right-click ContextMenu D-Bus method works, but the left-click Activate D-Bus method is sent and Steam does not respond to it.

This has been observed in multiple desktop environments and tray managers (tested with KDE Plasma, XFCE, and i3+polybar+snixembed), suggesting this is a Steam client-side issue rather than an environment-specific problem.
Related: #6186 (reported 2019)

Steps for reproducing this issue:

1. Launch Steam on Linux
2. Close/minimize the Steam main window (icon appears in system tray)
3. Left-click on the Steam icon in the system tray
4. Nothing happens — expected: Steam window should restore/focus
5. Right-click on the same icon — context menu appears correctly