I don't claim to know nearly enough about Siberian traditions to know what they say about this matter.
99% of what's on websites is wrong. So is just about everything written by Nuagers or would be leaders of the shamanism movement. Ib the rare instances when they are not completely wrong, they are often revealing things they should not, sometimes downright dangerous things like "how to do sweatlodges".
With anthropology books and other academic works, that's a complicated question. Some of them don't even like to use the word authentic, feeling it's too rigid and gives too much power to the anthro, who is almost always an outsider. The better ones have been debating for several decades among themselves if anthro books do much besides reveal the wishful thinking of the author. I have read some anthro books that do their best to be just faithful recorders of events and others words. So I would say that, as much as they could ever hope to be, they are truthful.
