If you are interested in a small Linux distribution which is a bit out of the mainstream, KaOS Linux could be just the ticket for you. It is independently developed, not derived from any of the larger Linux distributions, and it is absolutely focused on the KDE desktop. Just those two things really set it apart -- not just YAUD (Yet Another Ubuntu Derivative), and not available in a variety of desktops.
In addition to the KDE-only focus, KaOS has always strived to keep up with the very latest releases in the packages that it includes. That can be clearly seen in this release which includes Plasma 5.6.95, KDE Applications 16.04.2 and Qt 5.7.0 -- and by the fact that this release no longer includes Qt 4 or any applications built on Qt 4.
A new KaOS release (2016.06) was announced last week. However, because KaOS is a rolling-release distribution, if you already have any previous release of KaOS installed there is no reason to reinstall from these new images - just install the latest updates, and you will be the same as this new release. On the other hand, if you don't have KaOS installed this would be a good time to try it out, because there are not many updates to be downloaded after the base installation is done.
The ISO image is available on their Download page. One desktop (KDE), one architecture (x86_64), one fairly large file (1.7GB) with one MD5 checksum. We're all going to be good girls and boys and verify the checksum after downloading, aren't we?
There is a link to the Release Notes on the download page (oh, and right here too!). It is worth reviewing them, both to see exactly what is included in this release and to see what you might need to watch out for.
In case it isn't obvious when you get to the Download page, you start the download by selecting from the list at the left side of the window under ISO, either from the main KaOS download site or from a nearby mirror.
As you can see here, there are also some documents on how to create Flash or DVD installation media, along with an Installation Guide.
The ISO is in fact a KaOS Live image, so if you just want to try out KaOS and see how it looks and how it works on your computer, you can do that easily as well.
KaOS uses the Calamares installer, which I recently wrote about (Hands-on with Ubiquity and Calamares -- including complete screen shots), so I won't spend any time on that here.
When you boot the Live image you will get this 'Welcome to KaOS' window, with buttons to start the installation or access various kinds of help and information. Remember, though, that this is a Live system so you can do pretty much anything else, poke around and try things out to see how it works before deciding to install. If you happen to lose (i.e. inadvertently close) the Welcome window, you can still start the Calamares installer from the KDE menu.
One word of caution about a quirk in the KaOS installation: If you are installing on a UEFI firmware system, and you have experience with any other Linux installation on that kind of system, you probably know that the EFI Boot partition is usually mounted on /boot/efi/. KaOS is not "usual" in this sense - KaOS wants it to be mounted on /boot/. This shouldn't be a problem, because if you let the installer do the partitioning it will get the mount point right (duh), and if you choose manual partitioning the default mount point is still right. But if you think you are very clever, like I did, and you change that mount point to /boot/efi/, you will not be pleased with the results - the installation fails.
I have installed the new KaOS release on two of my systems so far - the Acer Aspire V5 and the Acer Aspire E11. As is almost always the case, the V5 was absolutely no problem and the E11 was a PITA because of its Broadcom WiFi adapter. I swear I'm going to turn that system into a Frisbee soon. The non-FOSS driver was not included in the KaOS base installation, but once I had installed the few updates that were available I was able to go into octopi (Add/Remove Software), search for 'broadcom-wl', then install that and reboot and all was then well. Of course to do all of that I had to have some other Internet connection. I keep an old USB-WiFi adapter on hand for just such cases, and the E11 also has a Gigabit wired network connection so that would have worked too.
One consequence of the absolute focus on the KDE desktop and its associated applications is that KaOS includes the QupZilla browser, rather than either Firefox or Chrome that most users are accustomed to.
If you don't like QupZilla or you absolutely want to have one of the others, firefox 47.0.1, google-chrome 53.0 and opera 38.0 are all available via Add/Remove Software (octopi or pacman).
The same is true of office suites; KaOS includes Calligra Suite. I know that a lot of Linux users will just automatically want to install LibreOffice (5.1.4 is available in the repositories), but if you are not a heavy-duty/dedicated LibreOffice user, I would encourage you to take a look at Calligra first. There is a nice Tour of the Calligra Suite on their web site. Calligra uses ODF as its native file format, the same as LibreOffice and OpenOffice, and it can read and write Microsoft Office file formats.
With all of the packages that are installed, and the rather large size of the ISO image, I'm a bit surprised that digiKam is not included in the base installation. Of course it is available in the repositories, and I got a pleasant surprise when I installed it and found that it is version 5.0 Beta! I use digiKam a lot, so I am always happy to get an early look at a new release. If you are a serious photo management / editing user, you will also want to install the hugin-tools from the repositories.
Being a KDE-focused distribution, KaOS includes the usual complement of KDE applications - Dolphin file manager, Kwrite/Kate text editors, Gwenview and Okular for image and document viewing, Spectacle for screen shots, Konsole terminal emulator and so on. They are all well-known from many KDE distributions, so I won't spend any more time on them here.
Another area where KaOS has made some very interesting choices is Multimedia. It includes the cantata MPD client (Music Player Daemon), mpv media player (a fork of MPlayer), and SMPlayer for audio and video playback (including the SMTube YouTube browser). Nice.
Just a few other details to wrap this all up. The new release includes Linux kernel 4.6.2, and it has 4.6.3 in the repositories as linux-next; it uses systemd 2.30 for system startup and service management; and it has X.Org 1.18.3 for graphic/display management. It uses octopi (GUI) and pacman (CLI) for package management.
I think that is enough for now about KaOS. As I said at the beginning, if you are interested in a Linux distribution which is rather unusual, not just another Debian/Ubunt/Fedora/Arch derivative, and you like the KDE Plasma desktop, you really might like KaOS. It installs easily, it works well and it is very well maintained as a rolling distribution it gets a steady flow of the latest updates. It is well equipped with a very good selection of applications and utilities, and in the places where the applications included are a bit out of the ordinary, it generally has the more common/popular equivalents available under Add/Remove Software.