I’ve been able to create a relatively passable version of ANH with no soundtrack for my own re-score of the film (using rock music that would’ve been released by '77 at the latest) by running selective channels of the 5.1 mix through vocalremover .org and then going through the “instrument” tracks to save any sound effects/ambiance I could. It was tedious and I had to manually add back in some sound effects to the battle scenes but it works well enough for playing around with re-scoring!