Issue:
After clean installation of Parrot Home 5.0.1, the window title font was showing as square boxes like [][][][][][][]
Resolution:
For me the problem was with permission, so after running below commands it got fixed.
find /usr/share/fonts -iname ‘*.ttf’ -type f -exec sudo chmod -v 644 {} ;
find /usr/share/fonts -iname ‘*.otf’ -type f -exec sudo chmod -v 644 {} ;
sudo fc-cache -r -v