Just finished both seasons of Sunderland 'til I Die. Found it captivating. I can't add much to what has been said on this thread. I thought Charlie Methven was intentionally channelling David Brent at times and enjoying the limelight, with his Ibiza pep rally the most obvious example. At first he seems a clueless corporate twat, but over time he seems more human and you start to see through the act. Stewart Donald seems a nice chap, but he needs to stay home on transfer deadline day and have a word with his wife about that makeup.
The fans came across as passionate but also childish and thin-skinned. As Graeme said, the editing of crowd scenes was a little misleading. I think the scene where they abused the documentary film crew and broke a camera was a revealing moment, as was the decision to show it immediately after a scene at the ex-army guy's house where he said they had the best fans, and that they deserved better. I think the film makers felt some resentment towards parts of the fanbase, and got payback by splicing scenes in an unflattering way.
Having said that, the tone of the documentary is sympathetic to the fans' plight and had me wanting them to do well, at least until the Brexit scenes. Having not known the outcome of games beforehand, I truly felt the pain of the EFL Cup final, and that last-second Charlton winner in the playoff. Brutal stuff.