Personally, I eat a fair bit of organ meats (liver and heart mostly) like a multivitamin. However, I don't know if that's really necessary; there are plenty of carnivores out there that do just fine for years at least who don't eat organs. I hedge my bets. But there are some well known 10-20 year carnivores out there that don't. And there are still indigenous populations that largely ignore plants.
Liver is wicked high in riboflavin which is involved in many metabolic pathways. Even the NIH can't dispute that it's the leader, even over "fortified" grains, which is laughable. I also recall reading or hearing that there is a naturally occurring congener of riboflavin in liver that isn't readily replicated in the lab, but can't seem to produce a citation now...
At any rate, I make a bone stock out of a couple of deer every fall and can it for use throughout the year. I include the larger bones as well as the liver and use it anywhere a beef stock might be called for. Deer shanks cooked in this on low heat for 4-6 hours is actual heaven. Haven't gotten into kindey, although I do save the kidney fat when possible.
I will take exception to the strict carnivore (and I see that you aren't really), solely on the basis that humans (and dogs, interestingly) produce both salivary and pancreatic amylase enzymes, both of which appear to aid in starch digestion. This might indicate that the ability to better digest starches was a previous evolutionary advantage.
I'm not defending twinkies and white bread, to be clear. But clearly we are adapted to consume some carbohydrates, and I don't think you disagree.
Edited to add that an evolutionary advantage and a dietary requirement might not always be the same thing.
I'm a food guy and really enjoy cooking, so my internal bias is going to rationalize a BLT sandwich with fresh tomatoes from the garden, an occasional few hot donuts from Southern Maid, and ice cream. I'll balance all those indiscretions with hideously painful calisthenics, cardio, and fasting as needed to maintain my insulin sensitivity and body composition.