Some people (such as myself) don't like the du command for finding out where disk space is used from the command line. I don't like it.
I like the many graphical tools available on the desktop, but sometimes I need to know where all of my disk space has gone on my server. And all I have is a terminal to see that from.
One of the best command line disk usage analyzers I've found is ncdu. It is a simple application that you can install on any Ubuntu system with apt install ncdu.
Running ncdu starts the program and it will run right away in whatever directory you started it in. See the screenshot to see how simply it shows you the distribution of your disk usage across your system.
It will show all the subdirectories of your current directory in order of highest disk usage to lowest.
Use the arrow keys to navigate the different directories and if you want to descend into a highlighted directory to examine the disk usage in that directory, just press "ENTER" and you'll get a nice display of that subdirectory's disk usage.
Basically, it's very intuitive to use. I don't think there's an easier to use disk usage analyer tool for the terminal than ncdu. It doesn't even need much more explanation. You'll figure it out.