Refer: https://itsfoss.com/create-custom-linux-mint-iso/
Refer: https://ostechnix.com/how-to-create-a-custom-ubuntu-live-iso-image-with-cubic/

Technical notes, and other ideas.
Refer: https://www.ostechnix.com/create-custom-ubuntu-live-cd-image/
Install Cubic
Cubic developer has made a PPA to ease the installation process. To install Cubic on your Ubuntu system, run the following commands one by one in your Terminal:
$ sudo apt-add-repository ppa:cubic- wizard/ release
$ sudo apt-key adv --keyserver keyserver. ubuntu. com --recv-keys 6494C6D6997C215E
$ sudo apt update
$ sudo apt install cubic
Refer: http://askubuntu.com/questions/47522/how-to-bypass-try-it-install-screen-when-booting-from-usb-live-session-wit
Release with updates installed:
http://old-releases.ubuntu.com/releases/
$sudo nano /cdrom/syslinux/syslinux.cfg
Replace:
# D-I config version 2.0
include menu.cfg
default vesamenu.c32
prompt 0
timeout 50
ui gfxboot bootlogo
with this for 32-bit:
default live
label live
say Booting an Ubuntu Live session...
kernel /casper/vmlinuz
append file=/cdrom/preseed/ubuntu.seed boot=casper initrd=/casper/initrd.lz quiet splash noprompt --
with this for 64-bit:
default live
label live
say Booting an Ubuntu Live session...
kernel /casper/vmlinuz.efi
append file=/cdrom/preseed/ubuntu.seed boot=casper persistent initrd=/casper/initrd.lz quiet splash noprompt --