This post is specifically about creating a new image from scratch to use with the Complete Linux Installer rather than using the ones that are provided for download in the app.
This is far from a usable experience. Notably, Android doesn't have an X server so you have to use VNC to get a GUI so a GUI is effectively useless. It's kind of handy to have proper GNU userland instead of Busybox sometimes and you can do silly things like run a local webserver and edit files using Emacs/vim/etc, but unless you're on a tablet with a keyboard attached somehow it's not practical at all. This has no relation to Ubuntu's efforts to make a proper port of Ubuntu to phones.