I’ve tried to summarize what little I know about probiotics in a series of posts [to be included here]. This is the post where I summarize my references.
Here are some resources that represent the consensus of mainstream organizations that do this sort of thing.
I’m not the first to compile a list of useful information about probiotics.
(Unofficial) Reddit Guide to Probiotics by a prolific Redditor who moderates the Microbiome forum.
Probiotics and microbiota composition (commentary) “Probiotics may promote homeostatis of the gut microbiota, rather than change its composition”