The first one that came to mind was fli4l (Floppy ISDN for Linux). Originally a distro of German origin that fit on a single floppy disk to turn a 386 or 486 PC into a router for ISDN connections. Last I looked it's still actively worked on.
There are probably tons of more obsuce ones. But this is one I actually used.
Check out the random button on Distrowatch (distrowatch.com/random.php) - it's like a Linux lottery, but you always win something weird!
Smoothwall. I used to run it a lot back in the early 2000s for personal use and even helped set up a couple small businesses with it but I don't hear of anyone else using it these days, people seem to love openwrt and pfsense more.
It was great for just taking any old x86 machine and making a powerful, fully featured firewall/router out of it, including a VPN server, all through a web interface. Nowadays that's boring shit but in 2002 it was pretty cool.
hyperbola
they have a wiki with insane nonsens about why they don't package certain things. Example:
pam
Package has different security-issues and is not oriented on the way of technical emancipation as Hyperbola is trying to adapt lightweight implementations.https://wiki.hyperbola.info/doku.php?id=en:philosophy:incompatible_packages
it's main feature is that it completely redefines the system's root directory structure. the only reason i even know it exists is because i'm friends with one of the creators
Have you ever heard of arch? That's what I use by the way
Rarely hear about DSL anymore, http://www.damnsmalllinux.org/
most obscure and to me coolest but unfortunately not very active https://sourcemage.org/
Take your pick from the Linux family tree
Bohdi linux. smoll and beautiful. Used to run it on my eeepc 701
Jarro Negro. Made by Mexican students. And as far as I know, it's independent, not based on another distro.
Well I don’t hear much about Gentoo, Damn Small, Puppy or Knoppix anymore. Wonder if they still exist.
I haven’t done much disto hopping since I settled on Ubuntu around ‘08 and then on NixOS last year. I like my systems working when I need them and waiting around for a new install to finish is boring to me.
I imagine there was a time when this wasn't obscure, but I'm guessing people today don't remember Caldera OpenLinux. That was the first Linux distro I installed/used. A guy from church gave his copy.
Caldera eventually became SCO. But I'm pretty sure I was using Caldera OpenLinux before the whole Novell patent suit thing.
Obscure as in "only for a very specific purpose and nothing else"?...
Well, there is the Mircrosoft linux distro for their azure cloud
I guess DD-WRT as distro for router is also kind of obscure. Or the more general openWRT for embedded systems.
The old PearOS(which looked like a meme-ish knockoff MacOS), UwUntu and Nyarch
Windows 11
Jolicloud. I ran it on an old low-spec netbook in 2013ish, basically a ChromeOS before Chromebooks were a thing. It was discontinued in 2016 but great for the hardware while it lasted.
Limiting to those I have used daily and treated as Linux (used the terminal for example) probably Maemo. I used to carry my Nokia Internet Tablet 770, and then my N800 everywhere with me.
Maemo is also an ancestor of both Tizen and Sailfish OS
I see no one has mentioned Bedrock Linux yet. Not sure though how others would rate its 'obscurity' though. It's definitely a standout among distros.
If being usable is a metric, Slackware
Sabayon Linux. I'm not sure if it's still releasing updates, the main website is dead. It was based on Gentoo and later funtoo, but had a package manager of precompiled binaries. You could still use emerge if you wanted to. Definitely a weird and interesting distro
Blend OS is trying to do the declarative nixos thing but with an arch base. That's pretty cool.
ClearOS was Intel's attempt at an immutable os. From what I remember it was really fast.
Edit: actually it clear Linux not clearOS. Edit: also clear Linux is stateless. I don't know, there's a lot about it I don't understand
There was a bunch of weird rebadged Ubuntu derivatives back in the day.
Ubuntu satanic edition. https://archiveos.org/ubuntu-satanic/
Ubuntu Christian edition. https://archiveos.org/ubuntu-christian/
Hannah Montana Linux https://hannahmontana.sourceforge.net/
United Linux - the famous Red Hat Enterprise Linux killer!
Clear Linux.
No one ever mentions Crux Linux
Not really a Linux distro, but TempleOS
dyne:bolic - specifically 1.4.1
Had support for the original Xbox, a multimedia editing / streaming focussed OS. I'd never run it on mine - just messed with xdsl before going back to XBMC.
I created a distro once for class that just had diaspora installed on a live CD. It was only used for demos a looong time ago. DiasporaTest.
Maybe not some obscure ones, but here are some lesser known ones:
Talos Linux. It's an immutable operating system designed specifically to deploy kubernetes.
OpenSuse Harvester Think Proxmox, but instead of VM's and LXC containers, it's VM's and Kubernetes.
XCP-NG is a RHEL based distro designed for managing Linux virtual machines using the xen hypervisor, as opposed to KVM. Think Proxmox, but RHEL and Xen (also no LXC). However, it does not come with a web ui out of the box, you have to deploy it yourself. Technically, XCP is a Xen distribution, since Xen is a kernel with nothing but a hypervisor that runs under the main distro, but the primary management virtual machine is RHEL based, and uses Linux.
Speaking of Proxmox, Proxmox is technically a Linux distro.
SnowflakeOS is a project that aims to bring a GUI focused experience to NixOS.
TurnkeyLinux (site is loading very, very slowly for me right now) is not a single distribution, but rather a set of debian based distributions that are designed to be turnkey appliance virtual machines that contain and host a specific app. To deploy the app, all you have to do is set up the virtual machine.
Now, here are some not-linux, but interesting distros:
SmartOS. They ported KVM to unix, and also can use Linux syscall translation (similar to wine) to run apps in containers as well. There is also Bhyve. It's a very interesting hypervisor platform.
OmniOS is similar. Bhyve, KVM, and Linux syscall translation in containers.
2 days ago my friend found an old SATA hard drive and gave it to me to check what's on it, and me, not having a disk station or anything, and against all better judgment, I just swapped the disk in my laptop for my friend's, and instead of my laptop being fried it turned out the disk was running something called Crunchbang Linux
I had no idea mageia existed until I met a dude who had it
BOSS.
One of the coolest distros, ever. It's like a mix of Alpine Linux and Slackware without dangerous firmware payloads.
I used to run Reborn OS at around 2017 for a few years. It used Cnchi installer, just like Antergos, and when Antergos died, I saw Reborn as its successor. But the title went to Endeavour (why?) and Reborn never got popularity.
templeos /j
Microsoft Windows.
Hot Dog Linux, X11 Window Manager with Windows 3.1 Hot Dog Stand, Amiga Workbench, Atari ST GEM, Mac Classic and Aqua UI
Not super obscure, but not many talk about it. Q4OS, I love it, a perfect windows replacement down to even imitating the old style windows installer. Plus it's Debian based so it has a lot of support. I plan on moving my grandparents to it when windows 10 gets fully discontinued as their current rig doesn't support 11
Feren OS, a linux distro focused in customization. Started as a Linux Mint derivative, is now based on Ubuntu and/or Debian (I'm not really sure)
Longene Linux. Linux-based operating system kernel intended to be binary compatible with application software and device drivers made for Microsoft Windows and Linux.
Shark Linux
Of those I'be personally tried, certainly chimera linux or mageia
Kiss linux. Gobolinux. They are both alien, but interesting, each one in its own way.
