It's not quite the same thing, but I've been enjoying using eshell (https://www.gnu.org/software/emacs/manual/html_mono/eshell.html https://www.gnu.org/software

It's not quite the same thing, but I've been enjoying using eshell (https://www.gnu.org/software/emacs/manual/html_mono/eshell.html https://www.gnu.org/software/emacs/manual/html_mono/eshell.h...). It has the usual shell interaction, except you can also interleave it with arbitrary elisp. It's not quite the OS, but it allows interaction with any parts of Emacs, which is at least OS-like (and can itself interact with the OS in various ways).