Chronic Fatigue and Probiotics?

Myalgic encephalitis (ME) and Long Covid are extremely debilitating conditions. They are often characterised by profound tiredness and 'brain fog' (a limiting of mental acuity). Some sufferers think they may have, inadvertently found a way of relieving their symptoms. These folk seem to have experienced a 'remission event' after a) taking an antibiotic for an unrelated bacterial infection and b) following this, by a course of probiotic supplements, The supplements were intended to restore the antibiotic-damaged symbiotic bacteria populations in their large intestine (https://www.theguardian.com/science/2023/jul/09/microbiome-chronic-fatigue-me-long-covid-research). It seems possible that the patient's microbiome (his or her gut symbionts) holds the key to relieving the chronic fatigue symptoms displayed by ME and Long Covid sufferers. Fairly obviously, much more systematic research needs to be done on this topic. The current information is somewhat anecdotal. It's been known for decades, that our gut bacteria produce vitamin K and some of the B vitamins. What else do they produce? Which bacterial species are producing potentially beneficial factors? There's a lot to learn about our 'friendly bacteria'.