Anecdata, but in my experience, my cognitive difficulties respond very positively to commonly recommended dietary supplements for cognitive disorders such as ADHD - particularly vitamin D3 and omega 3. Zinc and magnesium... not so much.

I have IBS - which could lead to nutrient deficiencies - and I've passed the initial pre-screen gate for ADHD assessment (coming soon). I also suspect autism, but the reward to cost ratio for assessment of that doesn't thrill me at the moment.

A different gut microbiome might simply be a way to solve nutrient deficiencies.