https://newatlas.com/science/multiple-sclerosis-gut-microbiome-genetics-bacteria/
The gist of the paper is that there is a connection between the two, but it's rather complicated. It's not as simple as 'this bacteria is good for you, this one isn't'. A species good for one person may be bad for another. From this I get the impression that there isn't an ideal FMT donor type; finding the right one for whatever problem you have is probably a matter of getting lucky. For a specific individual, an Olympic superathlete might be a worse donor than a couch potato.
Obviously more research needed.
The gist of the paper is that there is a connection between the two, but it's rather complicated. It's not as simple as 'this bacteria is good for you, this one isn't'. A species good for one person may be bad for another. From this I get the impression that there isn't an ideal FMT donor type; finding the right one for whatever problem you have is probably a matter of getting lucky. For a specific individual, an Olympic superathlete might be a worse donor than a couch potato.
Obviously more research needed.