I find white fish easiest to digest -- tilapia, cod, mahi-mahi.
I'm on a low-fiber diet until I get this flare under control, and my RD suggested congee (rice porridge). I made it in a pressure cooker with some ginger, carrots and mushrooms. The carrots and mushrooms are well-cooked so easier to digest. The various Asian cultures that eat congee will often add slices of fish or chicken on top of this. This can be done in a slow cooker or on the stove. She also suggested breakfast foods -- I recently developed wheat and dairy allergies along with UC, so I got some gluten-free pancake mix and made some banana pancakes with a side of scrambled eggs. Cream of rice with honey (I make it with unsweetened almond milk).
I'm sorry you're restricted so much -- it sucks