elementary OS
elementary OS is an Ubuntu-based desktop distribution. Some of its more interesting features include a custom desktop environment called Pantheon and many custom apps including Photos, Music, Videos, Calendar, Terminal, Files, and more.
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Vanilla OS
Vanilla OS, a fixed-release distribution based on Debian (formerly Ubuntu, prior to version 2) with the GNOME desktop, is an immutable operating system. The core parts of the system are locked down to prevent unwanted changes and corruption from third-party applications or a faulty update.