For Linux/Unix alike it’s a bit complicated as it depends on shell and terminal emulation. Which type of shell are you using?
I assume bash as this is most common, am I right?
In your Julia window, what do you see as title?
When you exit Julia with exit() is the window closed or are you at the shell prompt?
And if it is a shell prompt, what title do you see now?
(I don’t have a kubuntu at hand right now)