I can't speak about Chronic Fatigue, but I have had a period of illness where the fatigue was overwhelming and my appetite was zero.
Here are a few ways that I coped, you may have to adjust for your IBS limits:
Smoothies - what ever you eat can most likely be made into one (I haven't tried meat, but my all-liquid friend does chicken & turkey) My go-to was fruit, carrots, yogurt (my daughter uses non-dairy versions like coconut, soy or oatmilk), avocado, Garden of Life Organic Protein & Greens powder - blended on high speed. I would make a blenderful, and it made 4 meal replacements.

Orgain Protein Shakes (the non-dairy or dairy if you can)

Soups or casseroles - make when you feel good, freeze individual servings for reheating on bad days.

To supplement -

Any nuts you can tolerate - in butter form if you need - cashews are my choice

Yogurt or yogurt substitutes with peeled soft fruit like peaches or mangoes (I buy frozen chunks and mix in so they don't spoil on the counter)

Avocado topped with a little oil, dressing or vinegar

Eggs - we keep a few hard-boiled in the refrigerator

Rolled up sliced meats - I put a bit of cheese or pickle in the middle, or spread with mustard & roll up

Rice cakes topped with hummus/nut butter or carrots/pretzels dipped in hummus/nut butter

I hope some of these help.
Sue