There is a lot of misinformation about this at the moment.
Vit D supplements have not had any statistically significant effect on fracture repair (MDedge News Mengru Wang, MD, MPH, January 20, 2023) or in general ( www.medscape.com/viewarticle/968682) Taking it appears harmless but if you eat butter & cream or drink whole milk from outdoor cows (they need sunlight to make the vit D which is stored in the fats - so not skimmed milk), then you ought not to need supplements. Actually walking in daylight is just getting the light waves directly and you can make your own.
Other supplements may be useful in specific individuals (my DH is bad at absorbing vit C as a couple of people per hundred are. He gets mouth ulcers and we know it is time to boost vit C with supplements, or better, oranges and other fruits (not bananas but they give you potassium).
Vit B12 is usually short in vegans after a couple of years so they need to eat supplements or buy tofu, etc., but those are high carbon demanding and definitely not good for the climate.
Ultra processed foods are nutrient deficient is all minerals and vitamins, but high in sugars, etc. Not good.
Studies have shown that fructose without glucose is cancer causing so maple syrup is a problem there. That's why it was taken out of food for diabetics, where its ultra sweetness replaced a higher concentration of glucose so sweetness could be maintained with fewer calories.
Red meat is cancer causing so fish from sustainable sources is better for a couple of meals a week. Oily fish provide omega 3s
and can also be sustainably sourced. As milk / cheese provide protein, an egg or equivalent meat is enough for adults if vegetables are also eaten as plant protein can provide most of what we need - but not all. Children cannot be reared satisfactorily on a vegan diet. That's why the Japanese who moved to America, with its focus on meat, had taller children.
Most supplements are harmless but too much vit A will turn you yellow as do too many carrots - carotenes. You do need to eat a lot though.
So a rainbow (lots of different colours) diet, with skins on vegetables and most fruits, is the base.
Milk and eggs are produced by cows and hens to grow whole offspring so those foods only miss the vegetable fibre (to exercise our gut muscles,) from a totally balanced diet.