source mage linux.

Nobody even mentioned tinycore

I don't know if it's super obscure, but have not seen it mentioned here generally.

TailsOS

It's a built for the purpose of extreme privacy. It automatically routes all traffic through the TOR Network.

Check theleft and bottom of this tree too

https://upload.wikimedia.org/wikipedia/commons/thumb/1/1b/Linux_Distribution_Timeline.svg/3840px-Linux_Distribution_Timeline.svg.png

TempleOS should be obscure, but everyone knows about it because it's such a joke.

Less popular distros that I use are NixOS and FreeBSD. I haven't tried Gentoo yet, but I want to.

I want to buy a Framework laptop later this year. FreeBSD with KDE Plasma will be installed first, I might switch to Gentoo later, especially if work on the GNU Hurd kernel progresses far enough.