How do I boot into true text mode?

Edit in /etc/default/grub

# Stops the ubuntu purple screen
#GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"

# Uncomment to disable graphical terminal (grub-pc only) 
GRUB_TERMINAL=console

Then run a sudo update-grub.

To ensure 'that dumb purple screen' never shows up again after boot, do the following on the /etc/default/grub file:

• sudo vi /etc/default/grub
• Press i to enter into vi edit mode.
• Uncomment the line which reads #GRUB_TERMINAL=console by removing the leading #
• Press Esc to exit vi edit mode.
• Type :wq to save the change made to the /etc/default/grub file and exit vi

• Update /boot/grub/grub.cfg to have your change apply by running sudo update-grub
  
  

  If your computer uses systemd, you must tell systemd to skip the default login GUI thus:

• sudo systemctl enable multi-user.target --force

• sudo systemctl set-default multi-user.target
  
  
  
• Reboot your computer: sudo reboot

Now, 'that dumb purple screen' will never show up again.

Remember, you must update /boot/grub/grub.cfg to have your changes apply.