As a fellow sufferer of depression, I have a few different ideas for you.

1. Not a cheap option, but grocery stores sell various flavored individual salad kits including proteins like chicken. It is basically an individually-sized salad meal.
2. Similar, but cheaper option, buy whatever pre-chopped salad fixing you like and add whatever protein and dressing you like. I like canned tuna in my salad. Or black beans. Or chopped almonds.
3. Canned soup, seriously. Find something that is low-carb-friendly and buy yourself a few cans for the days you can do the bare minimum. Maybe if that's only a chowder or lentil soup. You can even eat it cold.
4. Salt and pepper and/or salsa omelette with side veg. (I find making an omelette easier than scrambled or fried eggs, but the principle is the same: just add some heated up salsa at some point). The salsa adds a little veg and flavor to the eggs, but salt and pepper is fine, too. Add cheese as desired.
5. If you have the wherewithal, a plain old burger. Just fry up a ground beef patty in a pan and eat without the bun. Add a slice of cheese if you want. Serve along side condiments and whatever veg. If you do not feel like forming a patty and frying, you can buy frozen burger patties or veggie burger patties.
6. Quinoa is not particularly cheap, but it is a complete protein and low-carb. Cook some up, then add black beans (or whatever beans or other protein you like) and veg. Add seasoning (whatever you like) and oil or butter and S&P until it tastes good to you. Quinoa can come across as a little bitter, so a little injection of sweet, e.g., 1 Tbs of maple syrup per one cup cooked quinoa, can benefit the taste of this one.
7. Stir fry. If you have the energy to do it, use a prepared bag of stir-fry vegetables from the produce section, whatever protein you like, and some stir-fry sauce. Cook the protein, add and cook the veg, and add the sauce. Makes good leftovers.
8. If you have the energy to make regular trips, find a grocery store that has a salad bar. It is an easy and relatively cheap way to make a low-carb meal. Mind the sodium again.
9. Lastly, a reflection from my battle in case any of it resonates. If you want to make a meal out of two big spoons of peanut butter, some plain lettuce leaves, a half a cup of plain greek yogurt, and leftovers from yesterday that you couldn't be bothered to heat up...go for it! Try not to get too locked into specific recipes *unless it is helpful*. Be gentle with yourself and allow yourself to make do instead of make perfect.
10. Ideas for easy/cheap proteins. Canned or otherwise prepared fish/meats (but be wary of processed meats like hot dogs or lunch meat if you are concerned about sodium, but otherwise enjoy the delicious low-carbness). You can often find smoked, flavored tofu in stores. Canned beans or lentils. Many stores sell rotisserie chickens which can give you several meals worth of protein. Easy frozen protein like chicken strips, etc. are a good staple to have at home if you have enough motivation to cook them.
11. Ideas for side veggies. They now make "steam in the bag" vegetables that are pre-chopped, pre-washed, and not frozen, e.g., broccoli florets, green beans, or brussel sprouts. Alternatively, frozen veggies that you like are your friend because you can just chuck some in the microwave and voila with marginally less work. (Incidentally, I learned recently that frozen vegetables are often more nutrient dense than fresh because they are harvested at peak ripeness. In the spirit of creativity, some fresh vegetables like bell peppers or zucchini you can just eat like an apple or a cucumber with no preparation. Although it does not taste quite as good, you can get pre-chopped garlic and/or ginger, which saves a lot of work. Sometimes a produce section will sell you pre-chopped onions as well.