Ubuntu Touch is a mobile version of the Ubuntu operating system primarily for touchscreen mobile devices such as smartphones and tablet computers.
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Pros
Pro Very privacy oriented, non-Google OS
No aggregating of your data or habits on any servers which you haven't requested (via apps, etc.).
Pro Many updates even for old phones
Getting updates every several weeks even in 2023, even if Android updates ended many years ago.
Pro Gesture based UI
Ubuntu Touch doesn't use any physical buttons, except for power and volume buttons. To navigate you swipe from edges of the screen. Swipe buttom-to-top gives a contextual menu, swipe right-to-left switches open applications, swipe left-to-right gives quick-access to apps, swipe top-to-bottom accesses notification center.
Pro Desktop/dock mode
Docking feature that allows to establish a PC-like desktop behavior from the mobile device was announced by Mark Shuttleworth.
Pro Quick-access settings
When swiping top-to-bottom to access notifications, you can (without lifting your finger) swipe to left or right to access different categories of settings.
Pro Screens hold information grouped together by topics
Ubuntu uses "scopes", functionality and information presented based on topics. Topics such as music, photos, video etc. Swiping left and right switches between these scopes. This information is pulled from various services used. So, for example, the music scope could consists of Spotify, Grooveshark and Soundcloud. The scopes can be customized.
Pro Converged desktop/tablet/smartphone
Shuttleworth estimates that desktop/tablet/smartphone convergence to be reached with Ubuntu 15.04 release.
Cons
Con Few mobile apps
Con Discontinued
Ubuntu Touch is discontinued and now not available due to lack of market share.