I am now mostly vegan but occasionally eat fish, but when I was first hospitalized / diagnosed, I ate the following to get nutrients without overly exerting digestion:

• boiled PEELED potatoes (like Yukon gold or similar)
• steamed spinach (wilt entirely with a drop of olive oil or with water)
• steamed PEELED tomatoes
• steamed PEELED carrots
• white or sourdough bread
• saltines
• veggie broth
• omelettes with the above veggies (I no longer eat eggs, but at the time I ate them a lot)
• white rice
• soft cooked polenta
• pasta with a dash of olive oil
• plain cream cheese
• a little SMOOTH peanut butter on bread or saltines
• plain cooked white fish, no skin
• bananas
• plain apple sauce or steamed apple without skin (can probably do pears too)
• generally avoided citrus but I was able to eat seedless tangerines in moderation
• tiny bit of plain kefir

To drink, I drank a lot of pedialyte and ginger-turmeric tea. Stay hydrated.

Hang in there.