How to set zsh as standard shell in Ubuntu
Install zsh
sudo apt install zsh
Add zsh to list of valid shells
sudo vim /etc/shells
Add to the list
/usr/bin/zsh
Set zsh as default shell
chsh -s /usr/bin/zsh
Double check
$ echo $SHELL
Now you might want to check out https://ohmyz.sh/#install to install a nice theme.