Of the Shatner movies, I only have 2, 3 and 4 on DVD. I bought them in a set called “Star Trek: The Motion Picture Trilogy”.
https://www.amazon.com/Star-Trek-Picture-Trilogy-Domestic/dp/B001TH16CY
I don’t know anything about where they were sourced.
I think those are from the bluray masters. I have the single DVD releases of 2, 4, and 6 from 2009 that also use the bluray masters.