breezeway VS syncthingtray

This is part of the testsuite of https://github.com/Martchus/qtutilities which you are likely building for https://github.com/Martchus/syncthingtray. It exercises the code to create notifications.

I also tried syncthingctl from syncthingtray:

Step 1: Download Syncthing & Syncthing Tray

My Syncthing Tray (https://github.com/Martchus/syncthingtray) can cope with Syncthing being started independently of it just fine. There's no installer, just a self-contained executable. If you use its internal launcher nevertheless (instead of a system service) then its auto start feature could cover Syncthing as well and you can start/stop Syncthing from the tray. (That is therefore the intended use on Windows where service integration hasn't been implemented yet).

I do agree that it could be a lot of effort to do it, though. I didn't necessarily want to bring this up because I don't want to take away from the fact that you made something, but there already is a Qt-based tray-centric frontend, Syncthing Tray, which does have an informative status icon. Is there a particular reason you made your own application instead of making a Flathub package for this one?

syncthingctl from https://github.com/Martchus/syncthingtray can wait for a folder/device/everything to become idle. Not sure whether it fits your needs. It is a non-graphical C++/Qt application (with no dependencies to X11 or Wayland that also uses the REST-API).

How did you install it? It doesn't seem to be in the official Arch Repos anymore and its python 2.7 dependency might be problematic. Try opening it from a terminal to get further debugging output. Since the Steam Deck is using KDE you might want to try https://github.com/Martchus/syncthingtray instead. (I'm the author of Syncthing Tray and would be interested whether it works on the Steam Deck. You will need to build it from the AUR, though.)

Syncthing-GTK is deprecated, there hasn'r been an update since 2019... Use something like https://github.com/Martchus/syncthingtray

I use this https://github.com/Martchus/syncthingtray

There are wrappers for Syncthing. Well mainly one actively maintained one at this point: https://github.com/Martchus/syncthingtray. There's also gnome shell status indicator(s). And syncthing-gtk, but I wouldn't recommend that: Someone at debian hosts a python3 compatible fork, which means it might be viable again, but there's no development there, so probably not long until it accumulates serious bugs: https://salsa.debian.org/debian/syncthing-gtk