From imdb: "Ten thousand years before Paul Atreides joined the Fremen to lead an uprising on Arrakis to take down House Harkonen, two sisters (Valya and Tula Harkkonen) create the mysterious all-female order called the Bene Gesserit. In Dune Prophecy, the siblings combat forces that threaten the future of humankind.".
Iirc, 10000 thousand years before Dune was the time of the Butler Jihad, when humankind fought against the thinking machines. So I think it's a series based on apocryphal stories on how the feudal society in Dune came to be. Lots of creative freedom for the creators, kinda like Knights of the Old Republic was for Star Wars.
Inspired by is not the same as based on. I don't think that it can ever be canonical because the time period was never explored in depth by Frank Herbert himself, but I do think that the what ifs of this time period could make for a very interesting premise.
Either way, the showrunner is apparently Alison Schapker, who was also the primary showrunner for Altered Carbon, which I really liked. So I'm definitely going to give the first episode a chance :)