I am installing Debian on an (old) Atom chip, i386 Kernel, and choose not to proceed with any GUI. Meanwhile, I see Gnome packages being installed. Is this normal? Why?
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You can get a full list of installed packages with e.g.
dpkg --get-selections | less.
If you selected to install a tool that has both text-based and GUI interface, it may have dependencies to some X11 and/or GNOME libraries. That is usually pretty harmless.
Also, with X11, it is perfectly possible to run a system with no display and no GPU at all, and still have GUI applications running on that system and sending their output to a remote display on some other system. That's why "no local GUI" does not necessarily mean "no GUI applications installed at all".