cf. https://dev.to/mskian/install-z-shell-oh-my-zsh-on-ubuntu-1804-lts-4cm4

http://grml.org/zsh/zsh-lovers.html

sudo apt update
sudo apt upgrade

sudo apt install zsh powerline fonts-powerline

git clone https://github.com/robbyrussell/oh-my-zsh.git ~/.oh-my-zsh
# Create a New ZSH configuration file
cp ~/.oh-my-zsh/templates/zshrc.zsh-template ~/.zshrc

# Clone the ZSH Syntax Highlighting
https://github.com/zsh-users/zsh-syntax-highlighting.git "$HOME/.zsh-syntax-highlighting" --depth 1
# Use the ZSH Syntax Highlighting
echo "source $HOME/.zsh-syntax-highlighting/zsh-syntax-highlighting.zsh" >> "$HOME/.zshrc"

# Change the default shell
chsh -s /bin/zsh
# Back to bash
chsh -s /bin/bash

To install Oh My ZSH, simply run

curl -L https://raw.github.com/robbyrussell/oh-my-zsh/master/tools/install.sh | sh