The Yakult company of Japan make these fermented foods things, calling the yogurts is a joke considering the ingredients. For decades they have been getting themselves banned by advertising standards for claims regarding beneficial bacteria that can't be backed up with science. Their product is marketing, yet millions believe their product works wonders - a placebo, if ever there was one.
I have an ongoing nutrition experiment, to cut processed foods and animal products from my diet. As a result, I cook from scratch at all times, even making my own bread. I don't use a fridge or a freezer since I don't buy anything that needs to be kept that cold.
What has surprised me is the absence of mold and decay. Before my experiment, I would regularly have to throw out lots of food that had gone bad, but now I don't have these problems. I thought modern preservation techniques made food last for longer, however, this has not been the case and I simply don't waste food.
In the article much is written about inflammation. Allegedly fermented foods help with that. But so does removing free sugar from the diet, along with processed foods and animal products. Therefore, before worrying about fermented foods, it is worth considering removing the junk first, as in all of it, to not eat HFSS (High Fat, Sugar and Salt).
A healthy gut is a huge upgrade to life and I don't think mine was healthy before my little experiment, but I knew nothing different, so I was not to know.
My advice for getting there is to cut the junk and cook from scratch, mostly, if not all, plants. Order should be restored to the gut microbiome with such a move, in a matter of days, no fermented foods needed.