Although the distinction between Dark Jedi and Sith is clear in Legends, the new canon version has redefined some critical underlying points.
In Legends, the Sith are considered to be the order of Dark Jedi who called Korriban their home and iconic birthplace. The early history is what defined their identity, however, particularly in the native Sith being their namesake, and the discovery of dark side knowledge while in isolation from the Republic that is inaccessible to normal Dark Jedi.
I'm still getting familiar with the changes made in the new canon, and I notice that Dark Jedi don't have their own canon tab in Wookiepedia, so I have some questions: 1) Is this history still valid in canon? 2) If the above is no longer canon, then is there still such a thing as Dark Jedi, or is Sith the new catch-all name for dark side Force users? 3) If Sith in canon are still (technically) a subset of all Dark Jedi as they were in Legends, and the old distinction is no longer canon, then what separates them today?