There are of course some niche distris that aren't based on the "big ones".
But I'm not sure Slackware is still at this point relevant enough to be named in a row with the others I've mentioned.
Of course the sampling was subjective, and I didn't intended to marginalize any not mentioned distris. I just thought the others are too niche to be included in such kind of pick.
Besides mentioning Slackware for historical reasons I should have also mentioned NixOS, which I forgot.
The former was the first Linux distri, the later gained some respectable user-base in the last years, I think.
Ah, and there is also Alpine which you can see sometimes here and there. (People using it in containers for reasons I've never understood as that's imho a recipe for trouble.)
But if you look at the rest of the list most of the stuff is really obscure. (I've tried some Solaris derivatives and Exherbo in the past but didn't even heard of all the other names.)
But I'm not sure Slackware is still at this point relevant enough to be named in a row with the others I've mentioned.
Of course the sampling was subjective, and I didn't intended to marginalize any not mentioned distris. I just thought the others are too niche to be included in such kind of pick.