Could you do Greek yoghurt on pancakes or something to try to branch out slowly?! We just do porridge every day (very occasionally Weetabix), but we mix up the toppings/fillings each day so it feels more variety. E.g. any fruit mixed in (frozen or fresh - e.g. banana, berries, apple, plum, pear), peanut butter, grated carrot, almond butter, dried apricot and nutmeg, cinnamon.
We usually do fruit and porridge which isn’t much help 😅 but she also loves an omlette which I usually cook in a bowl in the microwave for her as an easy breakfast, or scrambled eggs
My Lo absolutely loves weetabix in warm milk, occasionally he'll have a crumpet with a smidge of jam as a treat