I'm using default clean installation of Ubuntu with default settings of GNOME desktop (say 18.04 LTS).
> Did you try changing font by de-selecting "use system fixed width font" ?
Going to Preferences → Font & Colors → Font, and deselecting "use system fixed width font" substitutes font with other monospaced font - see image.
So this is not a solution.
I'm using default clean installation of Ubuntu with default settings of GNOME desktop (say 18.04 LTS).
> Did you try changing font by de-selecting "use system fixed width font" ?
Going to Preferences → Font & Colors → Font, and deselecting "use system fixed width font" substitutes font with other monospaced font - see image.
So this is not a solution.