It seems that ever since I've been updating my system the application icon that usually get's mapped to the window title bar has begun disappearing. This is happening on both of my systems installed with Fedora and Arch, on Fedora I'm running "KDE Plasma 6.4.5".

However I'm not sure at all if this is just a KDE thing or perhaps if it is like a new Wayland protocol KDE is early adopting. Maybe we now have to set the app icon ourselves programmatically instead of just assuming it will be set by the .desktop file.