Two changes I did like were Paul’s visions of possible future where Jamis becomes his mentor in the Fremen ways and friend, it greatly improved the scene where he sheds tears for a man he barely knew.
I also really love getting to see more of Beast Rabban and the effect he has on Arrakis. Imo that’s something that’s actually skipped over a little in the novel. Rabban is just someone who we mostly only hear about, his death is passed on as simple information as well.
The introduction was one of the pleasing additions that were made… We talked about it on a thread here about how could you show how the fremen wete repressed by the harkonen. Also the sigificance of the Arrakis palm trees which were originally going to be mentioned in the Lynch version first filmbook scene. This was done justice in the villuneve version and done well. Showing the burning palm trees too. The intro in the 2021 was going to be narrated by Reverend mother Mohim but it changed to be done by chani.
The other addition I really liked was showing Selusas Secundus and the Sandarkar. That was pretty cool with the throat singing and blood letting.