2.0 stereo sound mix, rather than a 5.1 sound mix.
The original 1977 release of ANH was in 2.0 stereo. I don't see why people that want the original versions should complain about that.
I wasn't alive in 1977, but some internet surfing tells me that three sound mixes were created for the film when it was first exhibited: a 6-track mix for 70mm showings, and both a Dolby stereo and mono mix for 35mm showings. I don't know enough about the movie to know how each of those mixes sounded, though.