When investigating gi dysbiosis with a metascriptomic stool test, how much can diet & supplements affect the result? are rx drugs (or fecal microbial transplant) the only proven way to rebalance the microbiome? or are dietary supplements an option?

Diet and supplements if you know enough could affect intestinal microbiome significantly. You are obviously knowledgeable in the area and with further research you would find how to use diet and supplements to treat GI dysbiosis. Fecal microbial transplant is not the only way to manage it and I know you are aware of probiotics and others that could be used. It is your diet that is most important.