Do you realize how pointless your question appears? It sounds like you will prefer anything that is unique and different. No matter if it is useful, makes sense, or is even as good as.

The world is full with product developers who long to quench the thirst of people who think like that. (And every possible thing is being done to amplify and create that demand).

To obey the marketing law of creative destruction, useful and mellow products are ceased all the time and are replaced with banana ware.

I am sure also in the field of operating systems. Just research and suit yourself.

Are we talking operating systems or user interfaces? The current state of OS's would seem to imply that evolution is working. We have what we have because it works. When something is found to work better, we'll change to that. Until then, we use what we like of what there is now.

UI's are a different animal. With the flap that MS caused by removing the start menu in Win 8/8.1 and Gnome with their version 3, and systemd with its surrounding turmoil, it seems to me that most people are willing to change to a point, but once they lose their favorite feature, they start pushing back and voting with their feet.

I'm as guilty as anyone else. If I ever lose the use of Ratpoison/Spectrwm/Tmux, I'll be one sad camper.

I take it you have not tried KolibriOS.

Just so you know, we have NEVER been limited to those choices. There were other useful operating systems before either linux or windows arrived, there have been other operating systems as long as they have existed, and there will always BE other operating systems. You just have not successfully sought them out yet.
CP/M and MPM-II still work, OS/2 is solid and wonderful if it is what you need (and SHAME on IBM for dropping support!), FreeDOS (with or without deskview) is incredible. In addition to these historical wonders and those mentioned earlier, there are new and different Operating systems that are more modern. Some of them previously mentioned, and few more obscure. Currently the Linux (and BSD) world is so exciting that it somewhat obscures everything else.
ReactOS and Haik* have been mentioned, and are very valid choices. I like where ReactOS is going and look forward to great things there.

In my earlier post I mentioned KolibriOS: an OS that is modern, small, unbelievably FAST because all of it is written in clean, simple, elegant assembler. It just SNAPS! But fast and nice as it is, it is only ONE of MANY.

eComStation is the bastard child of OS/2 with updates, new features, and enhancements to keep it current.

Syllable is the child of AMIGAOS, but with ported bits of other OOS projects including GNU.

OpenGEM is still running some look and feel of CP/M 86, with updates. IT can, I am told, run most of the FreeDOS suite.

Breadbox Ensamble is still going with the GEOS philosophy, but it is not free even to try.

Inferno is NOT Plan-9. But it ALMOST is.

SkyOS is no longer on my radar, but at one time was a very valid and different non-free option.

Last I heard, VisioPSYS was still available. Hard to get more different than that!

I am sure that will a well crafted search string you would find those and many more on Google.

Good searching ...

I'm not trying to be critical here but I sometimes run both Menuet and it's Kolibri fork just for amusement. What qualities of OS's written in "assembly" make them immune to hacking?

NOTHING is immune to 'hacking' or breaking! Period. But an OS written in assembly generally lacks all of those vulnerabilities generated by the behavior of higher level languages (such as C, C++, and C#) and the associated libraries. That makes it a lot less likely to be broken into than certain other operating systems.

BTW: some of the other OS options such as FreeDOS use an add-on sock or TCP stack and specific compatible applications to provide network services. These do not integrate network into the OS. This provides a significant separation and isolation layer and makes breaking into the system very different (arguably more difficult, but is anything difficult with enough knowledge).

Many of these alternative operating systems provide security as good as the very best secure operating system in the unix/linux/windows array for which the OP seems to want alternatives.

The biggest problem with them is that the applications and suites are NOT going to be those with which the OP is familiar!

With everything there is a learning curve. Has the OP the patience to investigate and learn another OS if he is impatient with those he is already familiar? Only the OP can answer that question.

Perhaps not but I do think unix variants will outlive most others.
Even Microsoft has gotten more into the unix like way of things, since Vista there have been a bunch of behind the scenes ways to make windows more unix like and by now one can use linux bash in windows thanks to the Canonical partnership.
If anything there will be no variety as there is very little right now due to you having just two major bases a mainstream OS is based on, the way thins look it seems that just maybe Microsoft is abandoning its old ways in some respects (marketing and some management aside) and is adapting itself to the unix way for better or worse its hard to determine.

https://libreboot.org/
https://www.crowdsupply.com/sutajio-kosagi/novena
http://playground.arduino.cc/

∞∞∞

Riiight. That's why there was no DOS malware.

(Seriously, what an incredibly strange thing to read).

I would be interested to know which vulnerabilities are these exactly, that assembly lacks. And is it linear? Does, say, Haskell have even more high-level language vulnerabilities?

There is nothing Unix-like on Vista, and one of the most common of Unices in 80's was Microsoft's Xenix.

Wine started in 93, i'd say there is much more incentive to make Linux more Windows-like.

Show me where anyone said that there was no DOS malware!

NOTHING is immune to breaking, but contrast the number of DOS threats compared to the number of Windows threats.
The worst threat I remember encountering on DOS was a boot sector virus on floppy disk: not really an issue today.

The very fact that you are running on an OS on which fewer roaches write threat software reduces the risk. (Never to zero.)

FWIW: I do have an idea for running totally threat free, but it is FAR off topic. Another time.

I'd hazard a guess that his theory is that if you write all the code yourself using assembler, then you won't have the inevitable bugs in the libraries that get linked in or called. Obviously, this is nonsense because it presupposes that assembly language programmers are perfect.

Plus, if that were true then there would have been no DOS malware. It's not a strawman to point that out.

There's RISC OS, and KolibriOS. I vaguely seem to remember finding a page on Distrowatch that linked to all sorts of obscure OSs, not sure where it went.

EDIT: Quite honestly I think the basic concepts of Unix are here to stay. It's been used since 1969 and it's still used in some of the most advanced technologies on the planet.
In D-Wave's promo video, they show a desktop that looks much like KDE (not saying it is, but just look at it). NASA is using Ubuntu. Even Microslop created a Wine-for-Windows deal to (sort of) run Linux software on Windows. The vast majority of smartphones run either Linux or Unix in some form or another.

Yeah. Unix isn't going anywhere.

Isn't that the threat that Secure Boot is supposedly protecting us from?

Note that most of those experiments were conducted or influenced by Dvorak.

Subsequent research has indicated that they were, at best, less than unbiased. But the myth lives on. . . .