I want to create several bootable Ubuntu 20.04 USB's with a bunch of programs installed. I want to automate this process, and not install plain Ubuntu and have to do the changes manually. I have a Docker image that is created by taking the default docker Ubuntu 20.04 image and making the desired changes. I thought I could use this Docker image to create the bootable USB. A quora thread, linked below, seems to suggest I am making a conceptual error.
So my question is: How do I create an image with preinstalled programs and custom settings? Can I use this Docker image, or am I wrong in thinking it is useful? If I am wrong, how do I create such an USB?