How can I reinstall Ubuntu

Question

I have a Dell XPS L520X that is currently running Ubuntu 18.04 Desktop. I want to update to the latest version of Ubuntu, which means that I have to reinstall it. However, I am having some problems with the installation.
The first thing I tried was installing Ubuntu 24.04 from a thumb drive. I flashed it with BalenaEtcher, then inserted the thumb drive into the eSATA port and selected eSATA in the boot menu. This didn't work, as when the Ubuntu loading screen showed up, it kept flickering back and forth from the loading screen to a terminal, and not actually loading. I then did a forced shutdown, but when I tried to load from the usb drive again, it just said "Operating system not found". I re-flashed the drive, but it still said that it couldn't find an operating system on the drive.
I then looked into installing Ubuntu without using external media. I tried doing what was suggested here, but UNetbootin didn't work for me, and I was unable to create a partition, as when I tried, I got an error saying that there was no available space for primary partitions. I was creating the partition in dev/sda, not the thumb drive. I also know that I was using the tool correctly, as I was following a tutorial.
If somebody could tell me how I can overcome these problems and reinstall Ubuntu, that would be greatly appreciated.
PS: this question is different from the other questions suggested, as I do not need to use the Ubuntu minimal image (my thumb drive has plenty of space) and the problem is not that I am unaware of how to install Ubuntu, as I have successfully installed it on other computers, the problem is that the methods I have used to install Ubuntu have failed.