Huh, I never knew of ARFID, but that fits me particularly well, especially as a kid. I will have to dig into this more.
For me, I found a relatively healthy comfort food (yogurt with granola; sometimes with berries) and have that for lunch most days. The granola makes it easy to load up on calories/carbs while it, and the yogurt, also provide a good amount of protein. Berries can add a bit of fiber. It's always delicious for me. I've been eating it consistently for years now and I've yet to get sick of it. However if you're lactose intolerant, this might not be a viable option.
Edit: reading the comments reminded me of another thing: protein shakes. I buy a container of whey protein mix from Walmart/Meijer and mix that with a glass of whole milk when I don't have the energy to make anything. It is delicious. The strawberry one tastes like strawberry milk and the vanilla one tastes just like vanilla ice cream but in milk form.
Water can be used in place of milk if you don't have any, or are intolerant, but it's nowhere near as good; it's just not the same.
It would be nice if I had more healthy comfort foods, but that's a work in progress.
Otherwise I supplement with a multivitamin to make sure I'm not deficient in anything.