Feedback on the Dell Precision 3590 (202312-33210)

I have purchased this laptop with a pre-installed Ubuntu 22.04 operation system. I wanted to add an additional partition with another Ubuntu to create an encrypted system, and so I created a Live USB Stick first with the latest Ubuntu version 24.04, then with the older 23.10 version which would still be newer than the pre-installed one, and eventually with the already installed 22.04 version. None of the iso files provided by the Ubuntu website would install correctly. They either would always mix the password I had chosen, so that I wouldn't be able to log in at all after installation (24.04) or wouldn't be able to get even booted for the first time after installation. I also checked several times that I used the correct passwords and followed the provided instructions (and spend almost three days trying to solve the issue on my own using the internet, fora and other articles).
I am wondering if the pre-installed version is different to the ones provided on the Ubuntu website for download and installation. And if this is the case, I am wondering, how I would be able to install an additional encrypted Ubuntu or even just the updated version on this laptop if the regularly provided installations wouldn't work in this Dell configuration. I already had a long phone talk with Dell Support, who eventually stated that as the pre-installed operation system works it wouldn't be their business but Ubuntu's to solve the problem. However, can you help me? - Is it possible as a customer of a Dell device with a pre-installed licensed Ubuntu version to receive an iso file that I can use for installing Ubuntu on my own on my laptop? Or would you have another solution for me to get the versions provided on the Ubuntu website work on my Dell laptop?