For me there has always been some food that I consider breakfast food, and food that I don't consider breakfast food. For breakfast, I eat porridge, cereal (most often a müsli blend) with yoghurt or milk, or sandwiches, often with fruit on the side.
Never anything that has been cooked, with the only exceptions being toasted bread or boiled porridge.
I should also say that I'm a vegetarian, but I eat eggs and dairy. Eggs, beans, rice, cooked veggies, etc. are only for lunch or dinner.
Then wth is Marmite made of?
Marmite is made from the spent yeast left over from brewing beer, and then there is lots of salt.
If you didn't grow up with it, you will probably hate it. I have tried it once - never again!