How do i install ubuntu onto a chrombook with out using crouton

DB Tech's video on how to remove ChromeOS and install Ubuntu from a USB drive looks like a pretty decent tutorial. In his video description, he types out each step:

Step 1. Enable Developer mode

Developer mode will wipe your Chromebook back to factory settings so make sure you back up any data not on your Google drive.

With your Chromebook turned off hold down the ESC and Refresh While keeping them held down, press the power button once.

Press Ctrl + D to bypass this screen.

Press Enter at the next screen.

On the next screen press Ctrl + D to bypass this message.

You will see a timer counting down in the top right hand corner of the screen. The Chromebook will reboot and you’ll see the screen with the red exclamation mark.

Developer mode is now enabled, power off the Chromebook.

Step 2. Modify the Chromebooks BIOS

By enabling developer mode, your Chromebook will always display the screen with the red exclamation mark on startup. Let’s now modify the BIOS to allow us to install Linux.

Turn the Chromebook on and press Ctrl + D to bypass the screen with the red exclamation mark.

Your Chromebook is reset to factory settings so you will need to go through the Chrome OS setup again.

Press Ctrl + Alt + T to bring up a terminal window tab.

Type shell and press Enter.

Type this: cd;bash ˂(curl https://johnlewis.ie/flash_cb_fw.sh)

** You'll have to replace that angle bracket with the one on your keyboard. YouTube won't let me use an actual angle bracket after the "bash"

Choose the option to Modify my Chromebook’s RW_LEGACY slot and follow the on-screen instructions.

Step 3. Enable USB boot

Pressing Ctrl + D at the screen with the red exclamation mark on startup will take you to your Chrome OS install but pressing Ctrl + L will take you to the BIOS screen to boot from your USB drive. Let’s turn on the Ctrl + L functionality next:

Press Ctrl + D at the initial startup screen to load Chrome OS. Press Ctrl + Alt + F2 at the Chrome OS login screen.

Login using the password chronos

At the terminal prompt, type sudo crossystem dev_boot_usb=1 dev_boot_legacy=1

Power off the Chromebook by typing in sudo poweroff

Now on startup, if you press Ctrl + L, you will get the BIOS screen instead of Chrome OS.

Step 4. Install Linux

At this stage most of the work is done and all that’s left is to install Linux:

Plug in your USB drive into the USB port of your Chromebook.

Plug in your live Linux USB into the other USB port.

Power on the Chromebook and press Ctrl + L to get to the BIOS screen.

Press ESC when prompted and you will see 3 drives: the USB drive, the live Linux USB drive (I am using Ubuntu) and the eMMC (the Chromebooks internal drive). Choose the live Linux USB drive.

Choose the option Try Ubuntu without installing. When Linux loads make sure you can connect to the internet (I am using my trusty USB to Ethernet hub combo for a wired connection).

Click on the Install Ubuntu 18.04 LTS icon and follow the on screen prompts until you get to Installation type.

We want to leave the Chromebook’s internal drive untouched so choose the option to do something else so that we can manually setup the partitions for Ubuntu.

Ignore all the mmc partitions and look for your USB drive, if you’re not sure, look at the size of the drive.

Check your partitions are correct and continue the install.

The rest of the install is a standard install so just follow the on screen prompts.

Once finished, reboot, remove the live Linux USB and press Ctrl + L You now have Linux installed. Run the software updates to make sure you have the latest firmware, drivers and software.