The Star Trek films haven’t had their 2 channels mixes in a long time. They weren’t on the last round of DVDs, Blu-Ray’s and won’t be on the 4K UHD releases.
Wish i could retire my Laserdiscs. I’m aware the 5.1 mixes are based on the 6 track mixes but that doesn’t mean the UHD release should be missing the original stereo mixes. For the oddest reason they are adding an isolated music track but no original audio?