Unfortunately there is not much information about the T-64U.
Here a little summary of the information i could dig out:
In 1999 there were three variants for the modification of the ukrainian T-64B/BV and T-64B-1/BV-1 tanks.
The prototypes were called T-64U.
A total of nine modified T-64 tanks were sent to the Independence Day parade:
Six T-64BV-1 with a mockup reactive armor. (1st variant)
Two T-64U (Object 447AM1) with reactive armor, modified gun, reloading and aim systems. New weather sensor. (2nd variant)
One T-64U (Object 447AM2) with reactive armor and modified internal systems, the same that were used on T-80UD (Object 478B) and T-84. (3rd variant)
All in one it looks like the T-64U had a different reactive armor on the glasic plate and the ERA layout on the turret was also different.
You can see the pictures here: https://dic.academic.ru/dic.nsf/enc_tech/4413/%D0%A2
The information on the site is from an russian modeling magazin from year 2000.
5. May at 22:10:46