Non-disgusting and Safe Ways to Seed More Gut Biodiversity

(Not sure where else to post this, since I don't really like r/health. I figure you guys are knowledgeable.)

I kind of foresee this post being crosslinked to r/fitnesscirclejerk, but hear me out. The modern environment is way to sterile, and I think it's one of the leading drivers behind the rise in autoimmune conditions, obesity, and mental health conditions. The immune system is out of whack, resulting in inflammation. How can we fix it?

Fecal transplants are the obvious option, but the medical community hasn't really developed it. You could DIY, but it is difficult to find a healthy donor, and it could be dangerous. It's also absolutely disgusting. So not viable yet.

Probiotics won't do it. Though they still can have many benefits, probiotics are transitory and dependent upon continuous pill-popping. Also, they cover a very small percentage of the strains that exist in a healthy human being. Kefir may be an exception.

Eating dirt is a hopeful option. A single cup of soil has a shit-load of bacteria. Instead of eating dirt, simply consuming unwashed, muddy vegetables straight from the backyard garden is a solid option. Despite the potential benefits to gut health, THIS IS POTENTIALLY DANGEROUS (not everything in the soil is friendly for us).

Lastly, simply playing dirty. I suspect that sex, kissing, as well as simply interacting with children, livestock and pets, can foster increased gut biodiversity. As far as I can tell, this seems like the best option..

If you avoided antibiotics, have a diverse diet with prebiotics, were breastfed, and born vaginally, your gut health is probably superb and you don't need to worry about this. However, just one round of antibiotics permanently alters the gut flora. What are your thoughts?