Best known as the open source Linux-based desktop operating system, Ubuntu is now making serious headway into the world of mobile hardware. And it's showing up to the party with a completely new approach to the mobile user experience.

The funny thing about Ubuntu's mobile play is that the user's main method of interacting with the phone doesn't rely on "apps" in the sense we've come to know them on our iOS, Windows, and Android devices.

Pick up an Ubuntu-powered phone and you'll find yourself dealing instead with "scopes," different topic-based collections where relevant information is grouped together. This approach is actually in-line with the trend we've seen across mobile OSes since Google Now showed up in Android, where top-level info in presented in easy-to-digest, topical sheets, cards, and other packages.

You can see it as soon as you unlock the Ubuntu phone and find yourself staring at the Today scope. It's the home screen, and sort of like Google Now, it shows weather, appointments, and other useful bits of information you can customize.

The Today scope in Ubuntu's mobile OS collects relevant information like the weather and the day's calendar, very much like Google Now. Maurizio Pesce

Swiping left, you flip through the other scopes on offer: NearBy, Photos, Music, and Video. You can rearrange their order inside a "Manage" menu that you access at any time by swiping a finger up from the bottom of the screen. Likewise, pulling down from the top reveals a notifications panel and main settings shortcuts.

Every scope is filled with information from various real-time web services. For instance, NearBy is geo-aware, so it shows traffic information for your current area while you're on the move, and displays different suggestions from Timeout, Yelp and Foursquare. The Photo scope is populated with pictures fished from the device's photo library, and your Facebook, Flickr and Instagram feeds. Music brings up songs you might want to hear based on your usage of Spotify, Grooveshark, Soundcloud, and Songkick. The sources in each scope can be picked and rearranged, and you can also create a new scope starting from a single source that you love—like a scope just for suggested YouTube videos instead of a generic "Videos" scope that pulls from multiple video sites.

So, where are the apps? Are they totally missing? Not really, but they're not front and center on your homescreen like they are on other OSes. They're listed alphabetically in the last scope. You can look for a particular app using the Search option that's present on every scope or access your favorite ones on the sidebar that slides in when you swipe in from the left side of the screen. At the bottom of this menu, there's an orange icon showing the Ubuntu logo: that's the shortcut to the home screen.

A quick swipe from the right side of the screen brings you straight to the last-used app. However, a slower swipe reveals a 3D carousel of all the apps that you've previously opened that are running in the background. Simply touch one to open it, or flick it up or down to dismiss it. Once you open an app, it runs in background until you close it from this multitasking screen. This screen is also the only way to switch from one app to another.

>The operating system uses "scopes," topical screens that collect data from multiple, related apps and services into one place.

It does take some adjustment. Personally, it took me a few minutes, but once I got used to Ubuntu's OS, I found it even easier to deal with than all the app grids typical of the other operating systems. For example, to find a picture I snapped yesterday, I didn't need to open three or four apps—Where did I post it? Facebook? Twitter? I just went to the Photos scope, and there it was.

Of course, a lot of services are still missing. There's no WhatsApp, nor Messenger. But Telegram is already here, and you can create a dedicated scope just like you can with every other app. In this case, the collection shows favorite contacts, last conversations, and gathers all the media files sent and received within the app.

Here's the camera in action. There are very few physical buttons on the phone, so to snap a picture, you just tap the screen. Maurizio Pesce

The hardware for the first-ever Ubuntu Phone is made by Spanish manufacturer BQ. The phone is called the Aquaris E4.5 Ubuntu Edition, and it's a midrange phone with modest specs: 4.5-inch IPS display with 960x540 pixel resolution at 240 ppi, 1.3 GHz quad-core processor, 1GB of RAM, 8GB of internal storage (plus a microSD slot), and a 2150 mAh battery. The main camera is 8 megapixels, the front one is 5 megapixels. Other than power and volume keys, there are no physical buttons, so photos are snapped by simply touching the screen. On-board software for the camera includes HDR, geotagging, and a 3x3 grid for helping with shot composition.

The Aquaris E4.5 Ubuntu Edition is currently available in Europe only through online "flash sales," so if you want one, you have to be—or know somebody who is— a) based in Europe and, b) very quick. Considering the price tag is €170 ($193.60), it's actually a pretty good deal, even if you're just interested in experimenting.

A second—and more technically capable—smartphone showcasing the mobile version of Canonical's open source operating system is expected to be unveiled at the upcoming Mobile World Congress taking place in Barcelona in March. It will be an Ubuntu-loaded version of the Meizu MX4, and it will be available across Europe in April, and in China the following month.