I have been a Kanotix user for about 14 years now, and it has been my main Linux distribution ever since. I tried a lot of others over the years, like Suse, Mandriva, Puppy, Dreamlinux, Manjaro, only to come back to Kanotix. The reason? It is rock stable, and it mostly "just works", and if you cannot get something to work, Kano himself & his crew are extremely helpful in finding a solution. Usually it is enough to go to the "factoids", copy the command(s) to a console, and bingo. Also, upgrades or dist-upgrades caused huge problems with other distros, to the point of completely breaking a nicely tuned system. This never happened to me with Kanotix, on the Debian jessie based version, run the script "update-to-stretch.sh ", and there you are! A lot easier than upgrading pure Debian yourself, and much better KDE preselections. The oldest hardware I run Kanotix on is a museum's piece, Thinkpad A30p from 2004, with a 1200 MHz Pentium III CPU, the most recent a Thinkpad T520 with Intel i5, plus an i3 Fujitsu Esprimo Desktop & a DELL E4300 Intel Dualcore. Minimum hassle to set them up, basic install takes 15 min., to set them up the way I like with all the bells and whistles (several e-mail accounts, exotic TV card, wacom tablet, wifi printer, VirtualBox, my own wallpapers, etc.): 2-3 hours.
Really worth a try, download the latest "Steelfire" nightly isos (KDE5/ LXDE) from here: https://kanotix.com/module-Downloads.html
A hidden gem here on Distrowatch.