I recall reading many years ago when I was making some kombucha that one of the problems was using a ceramic container that could leach lead into the brew - presumably related to the acidity of it.
Nowadays, I like to make kefir as that seems like the easiest fermentation - milk and kefir grains in a covered glass jar (not airtight) and leave for a day. Temperature isn't critical and there's no sterilisation needed.
Yeah I avoid porous things in general for that sort of work, but I remember hearing that the lower-end of Mexican ceramic crocks are particularly bad. I see a lot of lead recalls for Chinese products but it could just be because there are so many products coming out of China. When I'm doing any yoghurt type thing, I use my instant pot. Works like a charm.
Nowadays, I like to make kefir as that seems like the easiest fermentation - milk and kefir grains in a covered glass jar (not airtight) and leave for a day. Temperature isn't critical and there's no sterilisation needed.