I understood that after installing the seL4 first, and installing the linux later after seeing the 1.jpg.
However, in the “https://wiki.sel4.systems/Getting%20started%E2%80%9D.
“Setting up your machine - These instructions are for Ubuntu. They assume you already know the basics of using the command line, compilers and GNU Make.”
So then, Should I install the Linux(ubuntu) first, and install the seL4 later?
The "intended" way to build seL4 is to cross-compile it for the target platform (it might be possible also to build seL4 on the Odroid, but this surely makes things a lot more complicated). So install Ubuntu (or another GNU/Linux distribution) on your build machine to cross-compile seL4 there for the target platform you want it to deploy to.