Video of the result

Requirements

Having the chromebook in developer mode and crouton executable in Downloads folder https://github.com/dnschneid/crouton

I installed with: sudo sh ~/Downloads/crouton -t xiwi,extension,keyboard,cli-extra -r bionic

Crouton Launcher

fork from https://github.com/jmaris/croutonlauncher

Run Crouton apps as normal ChromeOS tabs on boot

This was tested using crouton installed with these commands: open a terminal with ctrl + alt + t

shell
sudo sh ~/Downloads/crouton -t xiwi,keyboard,extension,cli-extra,audio -r bionic

Install Menu:

Enter the chroot

sudo enter-chroot

Get the dependencies:

sudo apt-get install python3 python3-xdg git

Download the Software on chroot /opt

sudo chmod 777 /opt
cd /opt
git clone https://github.com/danielfm123/croutonlauncher.git
sudo chmod 755 /opt/croutonlauncher

Install the Chrome Extention provided in the repo by dragging to extensions menu in chrome, dots/more tools/extensions (remember to check developer mode)
Now you can launch executing main.py

/opt/croutonlauncher/main.py

Open with chrome http://localhost:8000 , the menu should be visible as a website.
Instal the extension First put it in the downloads folder with the command:

cp /opt/croutonlauncher/CroutonLauncher-Chrome.crx  ~/Downloads/

Then open the 3 dots menu - more tools - extensions , check developer mode is turned on and drag the crx file from Downloads the the extesions menu.

I recommend placing the extension pinned to the menu and configure as not a tab.

If you just want to launch the server from shell and not autostart the menu, the command to launch from shell would be

sudo enter-chroot /opt/croutonlauncher/main.py

Autostart on boot

adapted from https://github.com/dnschneid/crouton/wiki/Autostart-crouton-chroot-at-ChromeOS-startup

from chroot copy /opt/croutonlauncher/autostart to ~/Downloads

cp -r /opt/croutonlauncher/autostart ~/Downloads

open a shell (outside chroot) press ctrl + alt + t then open a shell (not a crosh)

shell

make root fs writable

sudo sh ~/Downloads/autostart/rw-rootfs

restart the chromebook

edit ~/Downloads/local/crouton.init on line 33 to put you chroot name default is bionic, might be xenial too
place files on system folders

sudo cp ~/Downloads/autostart/local/crouton.init /usr/local
sudo cp ~/Downloads/autostart/init/crouton.conf /etc/init
sudo cp ~/Downloads/autostart/init/mnt-crouton.conf /etc/init

Now you can delete Downloads/autostart

restart and profit from http://localhost:8000 or crouton launcher extension

danielfm123 / croutonlauncher