Crockpot meals are the easiest. I usually do chicken breasts with onion, carrots, broth/water, bay leaves, assorted spices of your choosing. Cheap, easy, healthy.

I usually bring protein powder (double bag that **** and get all the air out or get ready to clean up a mess) and a shaker cup. Protein bars also take up a small amount of space for how full they make you.

This trip I made split pea soup with bacon. It's pretty filling and easy/cheap to make.

My favorite is a crockpot/instantpot roast. Not as healthy due to fat content, but in moderation it breaks up the monotony of protein bars/shakes and the crockpot chicken.

Hmm, I'll add more as I think of things.

Also, invest in one or two good freezer packs. I'm not a YETI nut hugger, but their freezable pack is the best I've come across. I've tried 2 generics and one other that the wife bought. YETI is the best so far. If Ozark brand makes one it's probably pretty damn similar in quality and cheaper.

Edit: you're missing out if you don't have a crockpot. Most time effective thing to make enough of one type of meal at a time to last 1-2 full trips. They're cheap, like $35 for a big one.