I’ll dig in more but my first question when I see this: who are the donors exactly? Like who decides what the ideal gut microbiome is and that John Doe is the guy to provide his fecal matter to the masses?

Fecal transplants...people will do anything to avoid eating a balanced, largely/wholly plant-based diet with a wide variety of fruits and vegetables.

I would not recommend that site as a good resource.

Microbiome transplant therapy is a domain full of grifters right now who will push it to vulnerable populations desperate for hope, like parents of autistic children. The real research results are much less promising for difficult conditions.

There is zero evidence that poop transplants have any effect on autism, let's be clear here.