I installed kstars on a fresh mint 19. Starting Kstars displayed this message like in this
old post
Solved the above problem with like described in this post
The file citydb.sqlite could not be found. KStars cannot run properly without this file. KStars searches for this file in following locations:
/home/yourhome/.local/share/kstars
/usr/share/xfce4/kstars
/usr/local/share/kstars
/usr/share/kstars
It appears that your setup is broken.
Solved the above problem with like described in this post