UMPCs stand for Ultra-mobile PC. It's a rather modern term, used nowadays. Oh, I'm so excited about these! There is this childish feeling of owning a "high-tec gadget" - an all-in one all-purpose thingie, and carrying it around with you.
But, when it comes to actually using one - I have no idea what to do with them, actually. I believe, that's why nowadays UMPC's are considered "very niche" products and will never develop into something really useful.
All in one device
There are UMPCs that are actually trying to be a laptop - to look and feel like one. They boast long battery life and great specs, they have a keyboard and all that - plus a tiny size, like GPD Pocket series.
The main downside of these is the keyboard - and the problem is not that it is too small, but that is in order to make it small the designers always sacrifice some buttons. And these are usually the buttons I am used to, and the reason to use a physical keyboard in the first place - to blind-type. On top of that, English is my second language, and these keyboards never take other langues into account.
So, the only way to type comfortably with these is actually using a separate bluetooth keyboard (and maybe a mouse). But what is the point using an UMPC then, if it does not fit into your pocket?
Besides, that way the keyboard of the UMPC gets into the way. Some UMPCs actually did it great - they allow to flip the screen. GPD Pocket 3 even allows to act as a video INPUT - so you can connect another computer to it to use its screen as a monitor. That is actually so neat I am considering that device for myself (when they get obsolete and cheaper, of course...)
Pocket communicator
Well, I once thought it might be a cool idea - to replace my phone with something micro-laptop looking. With something that has physical buttons and a clamshell design. So I got myself a Gemini PDA.
These are really cool looking.. But they are actually crap. Dual-booting linux is cool, but neither linux nor their own flavor of android feels comfortable - the supplied software is clunky, the keyboard support is very limited. It just feels incomplete, imperfect. The thing is I expected the features that distinct that device from the others to be worked thoroughly - well, turns out the developers did not care much, the only thing they actually delivered is a phone with keyboard, that's all. A phone that is force-locked in landscape position so some android apps simply do not work (they support a landscape mode, but the device makes the apps think they are in portrait mode)
The worst part for me was the keyboard layout - in order to fit the keys they had to come with some tradeoffs, of course, but the keyboard is only usable for typing in english - even coding with it is horrible. Very weird layout. It would be okay if the keys were even smaller but there were extra keys.
And it has no highlight. Of course, we all type at 600symbols per minute with closed eyes, but hey, this one has a very unusual layout. Of course, I could force myself to get used to it - but I just don't see any reason to.
Besides, the hinge broke after first fall - it is very fragile.
After all, I realized my regular android phone (which is the Sony Xperia XZ Compact now) is way better as a communication device. Because Gemini just feels like a huge cellphone with a keyboard, and a very clunky one.
Playing games?
I do not play games, especially when on the go, and when I do I have a nice cracked Nintendo 2DS XL that works perfectly for that. Maybe one day I will try something like a SteamDeck or even a GPD Win, but that all is merely a toy.
That is not for actual... computing. Not something that requires a keyboard or a laptop appeal.
Hacky gadget
And what about having one just for the image, to be looking all-hacky? Well, I believe, there is a perfect device for that, called ClockWork PI DevTerm.
It seems useless for me, but looks way more "hacky" than any of the UMPCs. If I needed to debug stuff remotely, or to connect to CNC's, or maybe even to admin servers (physical servers) all the time, every day - it would be a useful thing, maybe, but otherwise it's just a pleasant and cool gimmick.
Everyday tool
After all, my all-in-one devices are my 13-inch ThinkPad and 13-inch MacBook. They do not fit into pocket, but have great specs and battery life. And great keyboards, that allow me to do anything I ever want to do with a keyboard, including typing this very article. I can work with these without any tradeoffs and with full comfort.
I always carry a backpack with me anyway, and it's a small backpack. I can even fit two laptops into it.