alt Hacker Newsthe null hypothesis for Voynich is that it was generated by some random process, like asemic writing, assembling bits from tables and copy/paste/edit. there are some reasons this is plausible (the entropy of Voynich words is low for language, there aren't scribal corrections etc), but fundamentally the "ancient hoax" hypothesis can't be proven, only disproven (since there's so much freedom of choice in generating garbage that it's not a compact explanation.)
so frustratingly, if it is an ancient hoax we can't ever prove it. all we would observe is that we haven't deciphered it, but failing to decipher isn't proof that there's nothing to decipher.
I recently read a good Voynich paper that makes me pretty sure that it was an ancient hoax. https://journals.openedition.org/digitalmedievalist/2331 The pages are more linguistically similar when read as flat sheets than when read as bound, and there's illustrations that stretch across the "gutter" between flat sheets that are cut off when looking at the bound manuscript. The manuscript was only bound once, in the fifteenth century (around when the pages have been carbon dated to). This means that whoever bound the manuscript was unable to "read" it, and the pages were likely written sheet by sheet before being bound in an arbitrary order.