My question is, let's say I installed software with a user interface, through the terminal. For example Synaptic (package manager).

Now, I've manually added a new .desktop file to the ~/.local/share/applications folder, with the following line:

Exec=synaptic # or Exec=sudo synaptic

If I didn't add the sudo command, I have a Synaptic window that says I don't have permissions. That is, you can view a user interface.
But after, the software falls off. Likewise, if I add the sudo command, the program immediately falls off without a graphical display.

Is it possible to run programs designed for Ubuntu Desktop without Libertine?
If so, what is the right way to do this?