Hi, that's a good question. Fibrosis is a consequence of a disease/condition and can occur in many organs. I think it's important to establish the cause first (viral/auto-immune/NAFLD etc.) and the mechanism leading to fibrosis (immune or non-immune mediated fibrosis and etc.). Regardless, there is definitely a role for the gut microbiome in fibrosis. I recently read this article below which I thought was great! I hope this helps.
Article Role of the Gut–Liver Axis in Liver Inflammation, Fibrosis, ...
The gut microbiota consists of various microorganisms that generally coexist in the human gut and maintain the host's homeostasis. However, once homeostasis is disturbed, metabolites
and components derived from the gut microbiota translocate to the liver and induce pathologic effects in the liver.
The mechanisms of liver inflammation, fibrosis, and cancer. Gut microbial components and metabolites; we include recent advances in molecular-based therapeutics.