Updated: September 21, 2020
Roughly two months ago, I embarked on my RPI4 home mini-desktop viability fun study, trying to decide whether the tiny board can be used as a general-purpose machine, providing a relatively cheap alternative to a full-fledged PC when it comes to basic tasks - browsing, media, whatnot. My initial testing soon exploded into a whole range of reviews and tutorials. My conclusion was, yes, you can do it, but there's a lot of work ahead of you, and you won't get an ideal video playback experience.
It's time to revisit my initial findings with Ubuntu MATE - there have been a lot of changes and improvements added both to the underlying operating system, the desktopify script that transforms the Server image into a desktop one, and the MATE desktop environment itself. Primarily, we're talking improved hardware support, with emphasis on 3D drivers. That's the theory, and now, the practice. After me.
Overall, it went smoothly - almost without trouble. Copy the server image to a 128GB card, check. Configure netplan so that Wireless connectivity works out of the box, check. Boot, try to login, no check. As it turns out, you need to wait a little for the default user to be created - otherwise the default user/password combo you expect will simply fail. This is a tiny but annoying snag.
After that, I cloned the desktopify Git repo, and ran the script. After about 40 minutes, the script finished. Reboot, MATE desktop, check. Login, lots of goodies, out of the box, check. No more overscan problems, so one less little hassle to worry about. Wireless connectivity also worked fine - MATE uses the existing netplan config, although you can delete it, and then reconfigure your network using the Network Manager if you like.
You get 3D support out of the box - but you still need to manually configure Firefox and VLC, and optionally Chromium, if you choose to install it as your secondary (or primary) browser. After that, I was able to get about 10-12 FPS in Firefox, and about 21-22 FPS in Chromium with the 500-fish Aquarium WebGL test. This is still less than what I get in Raspberry Pi OS, though (about 20%). Video playback is fairly smooth.
Very good. You don't need to mess with any configuration files. The audio panel has it all. I was able to manually switch between outputs (in my case monitor speakers via HDMI and headphones) without any problems. The only downside is: headphones were selected as the default, even though I didn't have the audio jack plugged in. It's a tiny issue, though.
Performance & heating
I noticed the desktop speed is solid - but there's some tearing (graphics drivers), which can create a sense of sluggishness. If you use Marco (no compositor), you will get a somewhat smoother experience, but then, you won't have transparency, which can be visually jarring if you're using the Plank dock - Cupertino layout. The Flirc box does tend to get fairly hot, so there's more improvement to be done, for sure.
Network speed is average (both in the 2.4GHz and 5GHz ranges) - the combination of the physical location and the shielding by the Flirc case result in a throughput of only about 40 Mbps, whereas most laptops in this same spot usually can do twice or three times that. Not bad, and definitely enough for HD content, but still.
Firefox scrolling is also choppy - but you can easily fix this by disabling auto-scrolling, which seems to be the default option.
I spent about half an hour polishing the visual side of things. I set the Cupertino layout - dock plus global menu, changed the wallpaper, changed the theme to use black fonts, installed some extra software like GIMP, VLC and dconf-editor, tweaked the window positioning, and a few other details. It was a relatively quick and painless exercise. Behold!
This time around, I have to say, the effort went much more quickly and smoothly, and I didn't have to fight the system to get the desired results. I am rather pleased with the outcome, and I can say, in its current guise, Ubuntu MATE does offer a decent, rounded desktop experience on Raspberry Pi 4. It's the most complete Pi operating system I've tried, when you take into account the functional, ergonomic and aesthetics elements.
At this point, I might be cautiously inclined to say: yes, here's your viable mini PC, right there. Of course, there's room for even more improvement - better 3D support, better performance, less heating. I think we will get there eventually. For now, if you'd like to try your luck with a card deck sized pack of punchy electronics, Ubuntu MATE is a sensible, pleasant choice for your Pi 4 adventures. And we're done.