SUMMARY All running Flatpak apps (whether autostarted or not) are missing their icon in the system tray since plasma update 5.27. STEPS TO REPRODUCE 1. Launch any Flatpak app, check if icon is showing in the tray OBSERVED RESULT No icon is shown in plasma system tray. In the "entries" menu, no Flatpak apps appear either. Other programs (i.e. installed via pacman) work as expected. EXPECTED RESULT System tray icon should show normally for Flatpak apps like the ones of any other programs. SOFTWARE/OS VERSIONS Linux: 6.1.12-arch1-1 (64-bit) KDE Plasma Version: 5.27.0 KDE Frameworks Version: 5.103.0 Qt Version: 5.15.8 ADDITIONAL INFORMATION Reinstalling apps and/or switching from X11 to Wayland does not change anything.
Apparently it was a conflict between SOME Flatpak apps and the latest Plasma update. Anyway, I was able to solve the most annoying missing tray icon (SynologyDrive) by downloading it elsewhere. As of today, other Flatpaks seem to work correctly.