Are you sure you’re talking about the Linux Terminal app that’s available in developer options and not Termux? For me, all Gnome things and Xfce things are present in the repos (and it’s using the deb.debian.org default Debian repos, so it makes sense)
I mean… This is kinda close. The “Linux Terminal” app is running a full Debian install in a KVM VM. On the newest version of the app (like on Android beta or on GrapheneOS), you even have a full GUI that you can use.
In theory, we should be able to boot any mainline Linux distro in a VM, if someone writes an app for it, as AVF (Android Virtualization Framework) is just a wrapper around Linux KVM with some restrictions. (for now the built-in app only supports Debian)
On Pixel 8 and above, you can plug in external displays, but it will only mirror your phone screen. Supposedly, Android 16 will allow you to “extend” the screen, ie. treat it as a separate screen. Also, the GUI stuff for the Linux Terminal will only drop in Android 16, so yeah, I’m stoked for that release.