click on application-menu icon in a panel without task manager right click on telegram icon select add to panel(widget) (if you have task manager add to panel(widget)doesn’t appear but you can drag and drop in the panel NOT in the task manager)
clicking on this icon should open telegram (as many other widgets) but it gives this error
Invalid service name: org.telegram.desktop (1)
in the system notifications
I also noted that also add to desktop doesn’t works
how can I get the telegram widget added to panel works?
Works here [1].
No issue adding icon to Desktop or Panel. Can launch clicking either icon. Might check for more details in logs.
[1]
From what I have read lately in your other threads, this is most likely due to your manual config changes/overrules. Even KDE will break at some time. What you can do is create a test user, login as that user and try if it works there. I would also suggest you read the KDE docs to see what changed from 4 → 5 and 5 → 6. The issue you are writing about here now, is the same as your other issues widget/panel related.