You have asked a very good question about fiber requirements for those of us who have diverticulitis.
Your doctor should, of course, be your guide in this matter of diet for diverticulitis. However, during an attack of diverticulitis, fiber should be eliminated until your symptoms are under control. Most of us, during an attack of diverticulitis, practice a liquid diet (or somewhat close to that) or very soft foods at least. For me, that includes liquid nutrition shakes, smoothies (without fiber), broth (bone broth is high in protein), etc. After the diverticulitis attack is over then I have soft foods for a few days, scrambled eggs, mashed potatoes, bananas, etc. I would like to invite @thull to this discussion as she has had lots of experience with diets for diverticulitis as well.