I am in Europe and it's the first time ever I hear about bulls spreading Covid to humans.
Edit - looked it up. Ah, so that's about the Chinese market trading exotic wild animals that was the ground zero of the outbreak. Never remembered that it had pangolins in the mix and I doubt that very many people do.
South Park did it. Probably NSFW
I suspect that, given we're a year on from the initial transmission of the virus in humans, unless the Chinese government has more research they haven't made public, we'll likely never know the truth.
My understanding is that there's really no evidence for it being the source at all; it's effectively a myth. It was an early super spreader, but there's no particular reason to think it was the _source_.