I’ll second the keto diet. I’m currently devouring a plate of porkchops covered in eggs.
My wife has severe ADHD, and she says she’s never so clear headed as when on keto. I am autistic with ADHD, and have had similar experiences.
We’re currently going back toward low carb/keto after the holidays. I just located an excellent source of local porkchops! 2 kilos for 13 EUR. I need a wheelbarrow.