Fyi kombucha isn't made from a "mushroom". It's a combination of bacteria and yeast and can be found in the liquid itself or the pellicle (blob of organic tissue) that forms during fermentation.
Well, it is a partly a yeast, which is a fungus, as are mushrooms. The main thing is that it is a symbiotic combination of particular yeast and bacteria strains, unlike what is used for brewing alcoholic drinks (just yeast) or fermenting dairy into yogurt (just bacteria).
Kefir is another combination of yeast and bacteria, though different strains.
https://en.m.wikipedia.org/wiki/SCOBY