last Frank Herbert book Chapter House Dune and from what I remember it was more like an underground society of Jewsish people who kept their beliefs completely unchanged over the thousands of years, as opposed to all the other religions and societies. I think it was politically organised along matriarchal lines but there were still male rabbis. I shoul read it again it's been decades!
The story line was really fascinating, especially the conflict and eventual merger with "The Whores".. However, when he wrote the last two books, beginning with the beautiful introductional ode to Herbert's deceased wife, .. it's clear his heart wasn't in it, and he was ready for the end (of either writing, or his days on the earth).
https://en.m.wikipedia.org/wiki/Chapterhouse:_Dune