The authors of Wrath & Glory, the official 40K pen and paper RPG, are working on a Darktide campaign where Grendyl sends the PC into the depths of Hive Tertium where they face “traitor forces of the Moebian 6th, cultists pledged to the plague god Nurgle, and strange lost sects of the Mechanicus”. The book / pdf will include a guide to the Hive and its history, a selection of hive encounters, and “rewards of gear and status from the mysterious Inquisitor Grendyl”. It’s due to release in Q3 of this year.
I do wonder on the canonicity of that (and the older Darktide board game). Having the pdf version.
Enemy mentions: Nurgling, Rotflies, an ‘Admech’ faction (not exactly the Admech, but it’s somewhat tied to them
Also GSC random encounter roll (but no lore/narrative tied to them, so difficult to say if they’re just random GSC that is far from establishment or not
THere are also some characters that on the discord we were wondering if they might be what Sefoni’s rumour are about, mostly about the Biologis Magos.