I want to cook different kinds of breakfast but I always use eggs because I feel it is easier to digest in the morning. What other kinds of protein could I use instead of egg? Some people recommend me to not consume any protein at all, but I feel I need protein in the morning, but something that is not heavy on the stomach.
How about fresh fruit with muesli/granola (which contains nuts and seeds) and yogurt (either dairy or soy)? That's my daily breakfast.
For example, this fruit, nuts & seeds muesli by Dorset Cereals (which used to be my favorite kind until I started making it myself) contains about 7g protein per portion (70g), and my favorite soy yogurt contains 5g of protein per portion (125g). Together they contain as much protein as 2 large eggs, and it's less of a hassle to prepare.
Buckwheat is also high in protein if you don't want to eat quinoa. It pairs well with fruits, nuts and raisins and can be a good alternative to oatmeal if you are sick of that.
I like a high protein breakfast too. You could try nuts, or fish instead of eggs and meat. Easy to digest seems to be very subjective, but I've heard that fatty meat and eggs are harder to digest than fish, nuts and drier meat (like veal).
If you let go of some cultural restrictions around what's ok to eat for breakfast you could be very happy eating sashimi, or even a nice curry in the morning.
I've also seen an interesting quinoa based breakfast (quinoa is relatively high in protein).