Gut microbiome researcher here - not involved in this study but happy to answer questions or dig in with anyone interested!
Is there a good way to test one's own gut microbiome? To determine how healthy it is or isn't, and to track how it changes over time. Basically I want to be able to tell how my diet and things like antibiotics affect it.
At a high level we know that diversity of microbial species in the gut (but for instance, not in the vagina) is linked to better overall health state. Is this because of the microbes? Probably not, it's probably that the microbes are a sensor/responding to an overall healthy diet/ecosystem.
In general, there are commercial services to track your microbiome and they are interesting from a data perspective, but I am not sure you will get much health information out of them.
We know the answer to a healthy diet - there are no microbial talismans - but it's just not sexy. Eat lots of plants, less sugar, and exercise. I wish it was as easy to follow this advice as it is to write haha.