Themes for Ubuntu GRUB

Find a theme you like e.g. https://www.gnome-look.org/p/1009237/

1. Extract the theme to /boot/grub/themes/

2. Edit /etc/default/grub file. Find the line starting with "#GRUB_THEME" and change it to "GRUB_THEME=/boot/grub/themes/[THEME_FOLDER]/[theme.txt]" (replace [THEME_FOLDER] ; [theme.txt] is probably OK ; remove "[]" brackets)

3. Run sudo update-grub

NB: The example given is in 7z format so you unzip it with 7z x grub_themes_stylishdark_0_1_by_vinceliuice-d8t31ig.7z.

It also contains a deb file that you can run to copy the right files or you can copy the unzipped files. However, you have to make sure you copy the right ones. It contains files like this:

grub-themes-stylishdark_0.1-1_all/boot/grub/themes/StylishDark/background.jpg

You want to go to /boot/grub/themes/ and copy the grub-themes-stylishdark_0.1-1_all/boot/grub/themes/StylishDark directory into it so you end up with /boot/grub/themes/StylishDark

P.S.: Grub themes usually come with appropriate install instructions or auto-installer. You can find lots of grub themes on https://www.gnome-look.org/browse/cat/109/ord/latest/

You can use grub-customizer. Run this in a terminal:

sudo add-apt-repository ppa:danielrichter2007/grub-customizer
sudo apt update
sudo apt install grub-customizer