Linux

Try to switch to console (ctr alt f2) and run xsession via startx. Or just try to install some meta package from console, like gnome-desktop (like sudo apt install gnome-desktop)

Anyway console (tty) is all what you have now and it should be rnough for restoring the system.

See if you can just re-install a desktop environment. Try sudo apt-get install --reinstall gnome (or maybe cinnamon-desktop-environment, whichever you prefer). Then reboot, see if that does anything.

You learned the hard way to always check what's going to be removed when using autoremove didn't ya. I did too, years ago. Must have been on Hardy Heron. It's a mistake you only make once... 😬

The solutions given by other people seem good enough. Reinstalling your Desktop Environment (in Ubuntu's case, Gnome) should fix it. But it's not all too clear what else you may have removed alongside.

Though to late to help you, when you get it working again, install Timeshift, so that instead of faffing around to try and suss out what went wrong, you just start timeshift -- restore from the console and a couple of minutes later you'll have your working setup back. It's saved my bacon quite a few times in the last couple of years, especially when you can't login to your DE.

Whenever you install or remove software, be sure to read through what's being removed. You don't want to accidentally uninstall something important. This is very unlikely to happen with official Debian packages, but you should be especially careful when installing packages outside of Debian's repo, as they may not be fully compatible with your version of Debian.

In any case, I'd log in to a tty (ctrl-alt-any function key) and install whichever desktop environment you had before using apt.

I recommend checking out Fedora Silverblue and other immutable distros, or, at least, use more containerization like Flatpak and Distrobox.

When the programs are all in their own small environment, they at least don't affect the base system like deleting the DE or other important packages when something goes wrong or changes dependencies.

But, in your case, try switching to tty (CTRL + ALT + F2) and installing the DE base (e.g. gnome-desktop). This will co-install all other dependencies, like X11.

Remember to always backup everything and reading thoroughly when using sudo in the future. And, maybe, check out the tips from my first paragraph :)