Como recomendado anteriormente na resposta a perguntas semelhantes , você pode tentar remover as barras de rolagem de sobreposição e alterar as propriedades de CSS:
#Step 1
echo "export GTK_OVERLAY_SCROLLING=0" >> ~/.profile
#Step 2
mkdir -p ~/.config/gtk-3.0
cat <<EOF > ~/.config/gtk-3.0/gtk.css
/* Adding the buttons on the edges (if you don't need them, skip the next 4 lines)
*/
.scrollbar {
-GtkScrollbar-has-backward-stepper: 1;
-GtkScrollbar-has-forward-stepper: 1;
}
/* Scrollbar trough squeezes when cursor hovers over it. Disabling that
*/
.scrollbar.vertical:hover:dir(ltr),
.scrollbar.vertical.dragging:dir(ltr) {
margin-left: 0px;
}
.scrollbar.vertical:hover:dir(rtl),
.scrollbar.vertical.dragging:dir(rtl) {
margin-right: 0px;
}
.scrollbar.horizontal:hover,
.scrollbar.horizontal.dragging,
.scrollbar.horizontal.slider:hover,
.scrollbar.horizontal.slider.dragging {
margin-top: 0px;
}
/* Slider widens to fill the scrollbar when cursor hovers over it. Making it permanent
*/
.scrollbar.slider.vertical:dir(ltr):not(:hover):not(.dragging) {
margin-left: 0px;
}
.scrollbar.slider.vertical:dir(rtl):not(:hover):not(.dragging) {
margin-right: 0px;
}
.scrollbar.slider.horizontal:not(:hover):not(.dragging) {
margin-top: 0px;
}
EOF
#Step 3
cat <<EOF > ~/.config/gtk-3.0/settings.ini
[Settings]
gtk-color-scheme="tooltip_bg_color:#ffffaf\ntooltip_fg_color:#000000"
gtk-application-prefer-dark-theme=0
gtk-primary-button-warps-slider = false
EOF
#Step 4
sudo apt-get purge overlay-scrollbar overlay-scrollbar-gtk2
Funciona pelo menos em 16.04 LTS com MATE DE.