Passover cereals made with matzah meal aren’t the worst, to me. I ate Blanchard and Blanchard granola and Savion Crunchy O’s this year, both of which weren’t bad. I actually very much enjoy Oberlander’s passover desserts, especially the rainbow cake, as well as desserts made with almond flour and almond paste. Osem cakes aren’t bad. Some of the pesach foods are good, others terrible.
The non-kitniyot cereals, non-gebrokts cereals probably are made with tapioca starch, since that is acceptable across the board for Pesach.