If I have the system tray in a latte panel I don't get a progress indication. For example when copying files with dolphin. The system tray is working (with progress indication) when it sits in a kde panel. For reference: https://www.reddit.com/r/kde/comments/jb83fw/dolphin_progress_bar_disappeared/
this is not related to latte.. remove anything related to notifications from plasma such as plasma systray in plasma panels, plasma panels, plasma systray in desktop, notifications widget from plasma panels/desktop etc... and relogin
one more comment is that 0.9.x is not maintained any more... 0.10.x is considered the in maintenance version.
Thanks for your response. I will do accordingly.