It is roughly 177 minutes long and adds nearly 40 minutes of footage. It features a new 10-minute prologue narrated by a male voice over still paintings, replacing Princess Irulan's original intro.
The "Spicediver" Fan Edit (Dune: The Alternative Edition Redux) Dune - Extended(1984)H265.mp4
Most viewers consider this an interesting curiosity but a "painful experience" that over-explains the plot. It is roughly 177 minutes long and adds