The release of Solus 4.1 Fortitude adds an official Plasma based variant of the distribution, the existing Mate, GNOME, and flagship Budgie editions. As the release announcement states:
We’re proud to announce a new addition to the Solus family: Solus Plasma Edition. Solus Plasma Edition has been a long sought after experience by current and prospective users alike, melding our ability to create a curated out-of-the-box experience with the sophistication of the Plasma Desktop experience. …
Solus is an independent rolling release distribution featuring its own package management system -- forked from Pardus Linux's PiSi package manager, and its in house developed GNOME stack based Budgie desktop environment. As the developers described it when Solus 3 was released:
This is the third iteration of Solus since our move to become a rolling release operating system. Unlike the previous iterations, however, this is a release and not a snapshot. We’ve now moved …