It is one of the files within the installer- and is content within the file. It is not a file named Ubuntu and I uhhh... realize now I cannot remember the name of the file.
It's been a while... And I commented off hand as I thought your issue was solved.
I did a search of posts on the topic of the forum as we on here have covered this a few times... Haven't found that particular technique but I did find a post from azorin re: Zorin 15, but should still be applicable: