I booted to xubuntu 17.10 and "kde-full", "kde-standard" and "kde-plasma-desktop" were not available.
However, in both antiX 17 and in debian 9 all three are offered.

Great Thread, esp for my learning. Thanks Mr... A few interesting links I discovered:
DistroWatch.com/Debian lists many DE options (Xubu 1); bbq 76! Wayland=future?

I think you install the kde package. Then, install a few complicated kde apps, like gwenview. That should drag in everything you need for kde.

edit, I can't find the kde package, but kde-full is in debian testing.

Wow this is really confusing, or maybe I'd rather say interesting: how exactly does this happen? I thought the package management systems would be the same. Is it just the repositories that are queried? Or are there distribution-specific changes to the actual dpkg client or apt frontend?

Not really. I would say I was unsure about how far-reaching distribution-specific changes to "base"-DE-frameworks are in packages such as kubuntu-desktop. However, this
seems to suggest that I overestimated by far the relevance of my concerns.
Just to get this straight, because this keeps popping up: I am well aware that an OS is far more than a DE, I am well aware that distributions ship more than the kernel and shell plus a DE, my concern was the assumption, that there ought to be some kind of a "pure" kde shipping, like there seem to be "vanilla" versions of xfce, MATE, GNOME etc.
Those might entail some additional configuring to do and all, but that's something I was kind of interested in doing anyways, since I am slowly reaching for a more thorough understanding of X and GUIs anyways, and how they live in the general shell environment. Ah whatever, thanks a lot folks, and I guess this topic's solved so far.
Happy you could draw something from this.

It happened back in 2004 when Mark Shuttleworth decided to fork (sort of) Ubuntu from Debian rather than simply using Debian's vast software repositories just like every other Debian based distribution up to that point. This has made a lot of people upset and some are still not over it (like myself).

The story's really complicated; the bottom line is that there's a lot of duplicated effort and a lot of weird diversions that Ubuntu has led down which had ultimately proved to be wasteful dead ends. And the "Ubuntu way" had for a very long time been to concentrate on just one desktop environment and simply prune away everything else...which lead to a bunch of Ubuntu based distributions with other desktop environments, and this stuff eventually got folded into the main Ubuntu repositories...bleh bleh bleh...look, it's a mess. And a really wasteful pointless mess because ultimately Shuttleworth lost his war to destroy Debian and replace it with Ubuntu maybe a decade ago.

So what do we have now? We have two big Debian-like worlds. The Debian world with its vast Debian software repository and the Ubuntu world with its own software repositories. These worlds have been close enough that some Debian/Ubuntu based distributions have actually switched from one to the other (and back!). At this point in time, it seems Ubuntu has shed most of its weird stuff.

But basically, if this stuff has you confused and confounded, then maybe it's time you jumped ship on Ubuntu in favor of Debian (or something else). Personally, I find Ubuntu perfectly usable now that it has lost most of its weird stuff. But then, I use XFCE4 and it's pretty much just the same on anything.

Just to add, you can have multiple desktops installed to a single Linux install and switch amongst them. Installing and removing a desktop environment or Window Manager will not harm your data or the underlying install in any way.

Slackware comes with eight desktop environments/window managers out of the box. Debian currently gives you the option of installing one or multiple environments out of the box--I have MATE and KDE Plasma on my Debian Sid (which started as Debian 9).

Mageia and OpenSUSE have integrated their distros with KDE a bit more tightly than have most distros, but you can still run other DEs/WMs on them. I have KDE and Enlightenment both on my Mageia Box.

I've run multiple DEs several times. The only downside is conflicting config files causing weird shit to happen.