In the U.S. or overseas? We know a Video CD exists.
From what I understand “Beyond Vision/Cult Classics” released a VHS version of THX and then a DVD (possibly overseas), based on Worldcat database and a few other sources. Additionally, there is a 1998 Warner Home Video Spain, a division of Warner Bros. Entertainment, DVD.
Again, I’ve read various databases which list THX as having been released on DVD before the bastardized special edition. Some of these sources incorrectly list the special edition as the original, which is easy to take off the list. But it doesn’t explain these other anomalies. However, I would take these sources with a grain of salt because I’ve never seen any DVD for sale, no pictures, etc. The only thing I’ve ever come across was an Asian VCD.