The Mystery of the Gnome Homes: https://www.youtube.com/watch?v=ZLoBWpiOczQ
The Jinx: The Life and Deaths of Robert Durst: https://www.dailymotion.com/video/x2xz5fs
I think all of Adam Curtis' documentaries are worth a watch:
https://www.youtube.com/playlist?list=PL617BE1DB723DB1D6
Some others favourites off the top of my head:
808 (about the drum machine): https://www.imdb.com/title/tt2268622/
Scratch: https://www.imdb.com/title/tt0143861/
Hoop Dreams: https://www.imdb.com/title/tt0110057/
Startup.com (a classic!) : https://www.imdb.com/title/tt0256408/
The Fog of War: https://www.imdb.com/title/tt0317910/
The Mystery of the Gnome Homes: https://www.youtube.com/watch?v=ZLoBWpiOczQ
The Jinx: The Life and Deaths of Robert Durst: https://www.dailymotion.com/video/x2xz5fs