There is Debian based and Ubuntu Debian based. Ubuntu as you may know is based on Debian, but then other distros are based on ubuntu, so it is more or less ubunutu underneath with a few differences. Mint and Trisquel as you said are ubuntu based, but then you can get distros based just on Debian itself, now they are a different thing, I was using Mint Debian edition and I loved it.
I had a quick look at slackware and you are certainly right it is a bit coarse, I had a look on you Tube on how to install it and it reminds me of the first time I tried Linux and gave up with Fedora.
This elementary is pretty good, it is fast, easy to install and use, not much scope to change the desktop, there is something called elementary tweaks, which I have installed, which allows me to change a couple of thing. for newbies who just want to brose and type a letter, it is ideal.
I will go back to mint Debian when the new version comes out.
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