gwookie

This one was rediscovered by the Internet a few years back but then disappeared off of YouTube. I just found it again on the Archive. Really good quality.

1985 PBS Nova S12E16 The Magic of Special Effects. Lots of stuff on the making of Return of the Jedi on there.
https://archive.org/details/TheMagicofSpecialEffects

I found a mother lode of stuff, most of the extras from the 2015 digital-only release of the Star Wars movies are posted here: https://www.youtube.com/c/LEKHANHProductionsLtd/videos

Some of the videos:
Discoveries From Inside: Models & Miniatures
Conversations: The Star Wars That Almost Was
Discoveries From Inside: Hologram & Bloopers
Conversations: Creating A Universe
Discoveries From Inside: Weapons & The First Lightsaber
Conversations: The Lost Interviews
Discoveries From Inside: Matte Paintings Unveiled
Conversations: The Effects
Discoveries From Inside: The Sounds Of Ben Burtt

and much more. Be sure to go through all of them!