The Dathomir Witches are seen among the various races visited by the Tho Yor in I think the first issue. They've long been established as being founded by the Dark Jedi Allya who was exiled to Dathomir in 600 BBY, some 35,000 years later.

Twi'leks are revealed in SWTOR as being genetically engineered by the Mother Machine, a device created by the surviving Rakata after their empire collapsed in 25,200 BBY.

The Wookiees are easier to handwave because the early history of their evolution has mostly been depicted as a matter of conjecture, but it's implied in Knights of the Old Republic that the massive foliage growth on Kashyyyk was caused by the Star Map in the Shadowlands malfunctioning after the fall of the Infinite Empire. Other sources already place Wookiees existing before that time though.

According to Evil Never Dies, the Rakata discovered the Sith and tried to conquer Korriban in 27,700 BBY, some 2,000 years before DOTJ, but there's a collage in the series showing the various Force-strong worlds that Xesh has discovered as a Force Hound and one of them is Korriban.