Meal Planner Apps

I never got around apps either since I try to spend less time on my phone and other devices. But it helps to have a basic formula in your head for a meal so it makes it simpler, mine is protein+ veggies since I am grain free.
A few ideas since I have been cooking mostly for one and packing lunches for 8 years through different careers and kitchens:
1) Freezer, I have a chest one which cost nearly nothing second hand and it saves me a ton of money on going out even with electricity bills: full of chicken, offal (I love liver, more nutrient dense and cheap), and occasional wild salmon (make it into gravlax and it will feed you for several days when you top avocado toast with it). Carcasses and skins go into freezer bag that gets made into bone broth that I freeze in muffin mould and pop out when I cook quinoa or make quick pureed veggie soup for quick dinner.
2) Pantry: eggs, canned tomatoes, olives and capers, sardines in olive oil, mustard, good olive oil for cooking and dressing, sesame oil for adding Asian flair, apple cider vinegar to add a shot into root veggie soups to cut the sweetness, tahini and honey (sometimes I eat them straight out of the jar, together, as dessert and total “halva”).
Eggs and tomatoes are a menu on their own - I make a quick sauce with capers, olives and anchovy paste for shakshuka, or dilute canned pulp with water and make a quick egg-drop soup with sesame oil and ginger for some Asian flavour (the best egg drop soup I had in my life was in Qingdao, China, when I lived there as student), fresh tomatoes can be fried with scrambled eggs and topped with cheese and dry basil (I still can't keep a basil plant alive long enough on my kitchen window).
Sardines with dijon are so amazing! Ultimate (grain-free or whichever) toast topper.
3) Slow cook and freeze - I make a ton of beef and butternut squash chili and freeze it, top with avocado, cheese and tortilla chips for extra deliciousness
4) Paleo muffins and quiches are amazingly filling and require some coconut and almond flour and eggs. They come together in minutes in one bowl, freeze well and contain a ton of high quality fat and fibre from the grain-free flours
5) Root veggies keep really well and can be cooked into pureed soups or roasted with some sea salt and spices, my favorites are butternut squash with rosemary and pine nuts and chipotle sweet potato oven fries
6) Cauliflower keeps surprisingly well! I keep it in crisper and make a quick puree with some of its boiling water and olive oil, or roast with mint, olive oil and lemon juice on a sheet for a few meals worth of sides.
7) Sandwiches: pick your bread and buy several loaves at the end of the say at any bakery when discounts hit, keep in the freezer. Pop a slice or two into toaster and smash avocado, mashed sardines with Dijon, just plain butter, salt and honey, or tahini+salt+honey (I love my sea salt on everything, haha).
8) I recently read about The Jar Method that apparently keeps foods fresh for longer, but it seems to require buying an online course which I haven’t gotten around to yet. Google it and see if it’s helpful!

I've been really happy with Plan to Eat. It is a paid app (I think there are free ones out there still), but it's been worth it. You can easily collect recipes from the internet (or add in your own collection), you can search for any ingredient in your collection (say you have spinach you want to use up), or search by various other criteria, it can easily scale recipes up or down, you can "drag and drop" to create meal plans, AND it can automatically create your shopping list ! I've really enjoyed using it the last couple of years.

Like Nancy, I also don't use an app but have a suggestion on using your produce. Change your order of operations: meal plan, then get your groceries. This way when you get to your produce you already know what you're going to make with it.

An indirect answer to your question. Not an app, but practices which will help you use & eat the produce you buy.
1) buy limited amounts...what you expect to eat in intervals between shopping
2) wash or prep all when you get home
3) put the fragile produce you intend to eat raw in containers easy to get at...
4) give (some or all) the sturdier produce a first cooking...then you have it to throw on a pizza, next to a piece of meat, into a soup.