There seems to be alot of similarity between the Navigator Guilds of both the 40K and Dune universes. Has anyone ever confirmed that one was inspired by the other (my guess would be the 40K version is inspired by Dune), or is there a similar organisation from fiction that could be seen as an earlier influence?
The Wikipedia article states that among others, Dune was a source of inspiration for Warhammer 40,000; though only specifically stating an inspiration for the God Emperor (Emphasis Mine):
Rick Priestley cites J. R. R. Tolkien, H. P. Lovecraft, Dune, Paradise Lost, and 2000 AD as major influences on the setting. [...] The Emperor of Mankind was inspired by various fictional god-kings, such as Leto Atreides II from the novel God Emperor of Dune by Frank Herbert, and King Huon from the Runestaff novels by Michael Moorcock. The Emperor's suffering on the Golden Throne for the sake of humanity mirrors the sacrifice of Jesus Christ.
While this does not specifically tie the design of the Navigators in 40K to the Navigators in Dune, the Fandom wikis all link this connection specifically:
The Guild Navigators have found themselves to be the inspiration for several creatures and characters in science fiction, such as the Navigators from Warhammer 40,000, the Advisors from Half-Life 2, the Aurora Unit from Metroid Prime 3: Corruption, quite possibly Melfina from Outlaw Star, the Cylon hybrids who serve as navigators and central computers in the Re-imagined Battlestar Galactica series, and the Tardigrade in Star Trek Discovery.
The concept of Navigators in the Warhammer 40,000 universe most likely drew inspiration from the science-fiction novels of Frank Herbert's "Dune" universe, being very similar to the Guild Navigators.
Unfortunately, outside of this, there is no link between Dune and the Navigators in 40K.