My default is one carbs+protein, one fruit and one veg and one “rubbish”.
Fruit = easy, whatever you have at home. Grapes, banana, melon.
Veg = easy, cherry toms, carrots, decanted sweet corn
Carbs+protein = pasta salad, sandwich, roll-up (Eg cream cheese, hummus, avocado, tuna, chicken breast)
Rubbish = granola bar, penguin, Kit Kat etc
I think you’ll be hard pressed to have a variety of non-UPFs that can be frozen and be a complete meal and provide a balance over the course of a whole term/month/week.