That looks like something I could buy. I've really wanted a tiny console PC with RS232 and ethernet for a long time now. I thought about building one into a custom keyboard using something like a raspberry pi but I haven't had the time to follow through. This thing looks like it could make my diy project unnecessary.
I also haven't found phones particularly appealing.. mine gets 5-6 days on a charge because it's mostly just an alarm clock. Any time I try to do anything with it, I get frustrated by how clumsy it is compared to an actual computer. I do like being able to look at maps or make a call in an emergency, and it's handy having a camera always in the pocket, but that's pretty much where the appeal ends.
Battery replacement is a matter of unscrewing the case. It's glued to the interior, but I've seen teardown videos of people just peeling it off so it's not a big deal. In lieu of hot-swapping batteries, I sometimes carry a USB-C PD power bank - although the Micro PC is low power enough that it will actually charge off a regular phone charger.
First, the keyboard: The Cosmo keyboard is not designed for thumb typing. You can do it, but it's a bit awkward. The phone is not comfortable to hold in this configuration - it's thin, wide, top heavy, and the hinge has sharp edges. The generous key travel also works against you when thumb typing. It seems that you are basically always meant to put the phone on a flat surface and touch-type - but it's not very good at that either. It has no feet on the (slightly curved!) bottom surface, and while the rear hinge is meant to act as a kind of kickstand, the design means that force of typing transfers to the screen, causing it to wobble with every keystroke. The keys themselves are as nice as is possible in that size, but touch-typing at a table while on the go is a very narrow use case. The device feels delicate and fragile. Also - while this isn't a completely fair comparison as I've only had the GPD for two months - after a year the keyboard began missing keystrokes (and this was a replacement keyboard, since the one it came with did that from day 1).
Next the screen - a super-high aspect ratio smartphone screen turned landscape is actually really annoying. You have almost no vertical real estate, whereas most phone apps assume that the vertical axis is where all the real estate is and consequently put menu bars at the top and the bottom, eroding it further. There's very little gap between the touchscreen and the keyboard, so accidental touches are common. Switching between touchscreen and keyboard interaction is even more annoying that switching between mouse and keyboard on a desktop, either because you have to transfer the weight of the device to one hand if you're holding it, or if it's on a table because you must gently prod at the screen without tipping the thing over, or brace the screen from behind. Also the screen only opens to one very wide angle (cheerfully described by Planet as "the optimum angle"). There's volume buttons, but they're awkwardly on the back of the screen, which would make sense if they worked when the device is closed, which they DON'T.
Now, the GPD Micro PC: no touchscreen, which is actually great because all interactions that change the state of the device require definite action and make a physical "click" - you don't have to worry about accidentally brushing it the wrong way. This actually takes a lot of cognitive load off. It's comfortable to hold in two hands for thumb typing (but also has rubber feet so you can set it down). The touchpad is accessible with a fractional movement of the thumb, so switching time is minimized. There's dedicated and easily accessible volume buttons. The screen has a comfortable aspect ratio and can be set to any angle, where it remains stiffly. And most importantly, it runs desktop software. With these controls, it's more ergonomic to use desktop software in miniature than it is to poke about at a touchscreen.
I was never brave enough to tinker with GNU/Linux on the Cosmo while it was my daily driver. I'm pretty sure that using the device that way comes with some pretty sever compromises.
On the Micro PC, I run Void Linux with KDE Plasma. I didn't do anything special, everything's mainline, so I'm sure at a technical level Ubuntu MATE would work perfectly well. The only interface tweaks I've made are to set the task manager to "icons only" to save space and added thermal/RAM/CPU monitors in the taskbar.
As for "toy gadget" vs "useful tool", I'd say that if you're the kind of person who likes to take your laptop everywhere, it's definitely for you.
I struggled to find honest reviews of the device so much appreciated.
It seems pretty under powered to me. What exactly do you do on it?
Quad core and 8gb of RAM is underpowered? It's not the best gaming machine to be sure, and I have to be a little more careful with my browser tabs than on my 64GB workstation... but there's not really anything glaring it outright can't do.
Hard to answer what I do on it, since the answer is "everything". I run Plasma 5 on mine. Right now I have a lot of firefox windows open, Quassel (IRC), Qalculate, some file managers, some terminals, and some text editors. For heavy duty I sometimes remote into my workstation (graphically) which is fast enough on a LAN to use CAD and all the rest of it. I've even done ANSYS simulations this way.
It's a magical size - exactly small enough to slip into a back pocket like a chunky phone, and exactly large enough that it's actually practical to use desktop software on it. It's ergonomically first-rate - I've done CAD work on it. And it's durable too - I've dropped it several times already and it's barely even scratched.
It's also unlocked a class of activity I didn't know was possible - long-form writing while out walking. I can get 50wpm with great tactile feedback on the tiny keyboard. It's all in on thumb typing, and having struggled with a Cosmo Communicator for a year I can absolutely say that that is the correct decision for a mobile device. The vast majority of the time there's no handy surface nearby.
Now that I essentially have a laptop on me at all times, phones hold no appeal for me anymore. None. This is the class of device I've always wanted. All it really needs in order to replace a phone completely is a cell modem which can wake it from suspend, and ideally the standard "mobile" sensors such as GPS, cameras, and gyros. And waterproofing, I guess.