We discovered a cut that was about three hours that people who hadn’t read the book seemed to understand. Had a different intro and flowed better.
I’ve seen three versions of this movie. The theatrical and the longest one both sucked for anyone not a Herbert fan. I thought the longest was the director’s cut but he never did one. Perhaps it was the TV movie cut. But I don’t know what the “good” one was called.
This page on IMDB has all the "legitimate" versions I'm aware of, but I'm sure there are unauthorized cuts out there:
https://www.imdb.com/title/tt0087182/alternateversions/
A non-theatrical "director's cut" is a Mandela Effect moment for me. I don't know what I watched. It wasn't the TV version, because that was the first version I watched. I can only guess that it was a common mistake to call some version "the director's cut" among viewers (or maybe just my friends) in the past.
The list I've linked to certainly wasn't illuminating for me, but maybe it will be for you.
Interesting. I understand he wasn't satisfied with the introductory narrative and other non-cinematic means of storytelling. But I love how the movie focuses on inner dialog to approach the novel and how decidedly non-techie, for sci-fi of all things, the movie was at the time, believably telling the story of a post-tech society that had room for style and decadence. And the Dune remake pays tribute to it.
I was also in awe how time travel was depicted by music; might help that the cheesy guild navigator scene operating the spacecraft wasn't shown (or was it? I didn't notice it when I first viewed it, and I like to think that's one of those scenes David Lynch would've rather left out).
I camped out in line on Hollywood Blvd for several hours to be in the first public screening of Dune at the Chinese Theater. So I know I saw the release print and to my then college-aged perceptions, I didn't really connect with it. I didn't think it was bad but I didn't think it was good either.
I blame this on the muddled mess that was the release edit and how misleadingly the film was promoted by the studio. I was a huge fan of pop sci-fi like Star Wars, Alien and Blade Runner and the advertising set a very different audience expectation than what the film delivered. Unfortunately, that experience kind of tainted Lynch's Dune for me.
I didn't really begin to appreciate Lynch as a great filmmaker until Blue Velvet and Twin Peaks, both of which I loved. Someone linked a 'highly-regarded' three hour fan edit of Lynch's Dune which I've bookmarked to check out.
My best guess is that you're thinking of the Spicediver edit, a fan edit which runs about three hours, and is highly regarded.