Yes...chickens are "meat eaters". They'll catch anything they can and eat it raw.
I often offer them high quality (grass fed), raw ground beef or venison, chopped raw liver (beef or venison) and any other meat protein I can get for a reasonable price. They get mealworms and any other bugs I can get. I've never tried to raise the black soldier fly larvae because I'm not sure we have them here in the summer. But I know another person that does them and puts all the summer harvest of the larvae in the freezer so they have them for winter.
When I bring out ANY meat or bugs, they go absolutely bonkers. It's like they are totally starving for meat.
You will find that, if given a choice, chickens will NOT eat legumes.
Legumes are not one of their natural foods. And
many of the legumes (including soy) are toxic to them unless they are roasted. (Soy continues to be toxic even roasted, but the roasting does help reduce some of the toxin.)
It you think in terms of natural,
if something is toxic to an animal unless it is roasted, you know for sure it isn't something they should be eating (As I've said before, I've never seen them build a fire and roast anything around here
In days gone by, chicken feeds did NOT contain legumes. If a commercial feed was purchased it contained meat and bone meals, corn, oats, etc. But not legumes. The addition of legumes started with industrial farming. It "cheapens" the feed for the consumer and is a good way to make money on waste products from industrial farming (soy bean meals, oils, etc.) that they have a hard time using anywhere else. One of the bad things about this is that there are many anti-nutrients in legumes that inhibit the absorption of minerals especially...and actually leach them from the body. This is another reason that we have to add a mineral mix into the feed. Even though the minerals are there, they aren't bioavavailable from the legumes and/or seeds so only a very small portion is absorbed - if any at all. This is the same for human ingestion btw.
Okay...off my soapbox.