You absolutely should not eat less than 1000 kcal a day in oatmeal only. Occasionally, it’s not a big deal but consistently it’s not healthy.
I do 20:4 but tend to do a little granola with yogurt, let it settle, and then essentially an OMAD salad. I can vary what vegetables are mixed in, what protein I add to it, what dressing I use. I like it because it keeps my shopping list simple but allows me to mix it up if I get tired of a certain flavor profile. this week I’m doing panzanella!
I should add the caveat that I am, on the whole, a “food is function, not fun” person and have a high tolerance for repetition in taste and texture,