It's listed as an upcoming April addition to the streaming service. The Story of The Faithful Wookiee which features Fett's first ever on screen appearance will officially become part of the Disney catalog. The Nelvana animated bit was a segment during the special which saw Chewbacca's offspring Lumpawaroo watching a program that featured Fett's premiere.
Although the bit was a hidden Easter egg on the Complete Saga blu-ray edition, it will now be widely available for the first time as part of the Disney+ library.
Also announced were the additions of The Ewoks cartoons and The Ewok Adventure movies which first appeared on ABC television.
-CG