The vellum of the Voynich Manuscript has been dated to the first part of the 15th century, though it has been noted that the text could have been written later.
This was the time when movable type printing was being developed (see Wikipedia page [1].
Roger Bacon, having lived in an earlier period is thus excluded from being the author of the VM, as are the Cathars.
There were a range of manuscript hands in use at the time - and a number of scripts (Latin, Greek, Cyrillic etc).
Prester John was believed to be in Africa in this period.
Various 'heretical' movements were developing in this period - notably John Wycliffe and Jan Hus.
Early 15th century: beginning of Portuguese exploration and expansion - capture of in 1415 Ceuta.
1440 Lorenzo Valla published a dissertation against the Donation of Constantine.
In the mid-15th century Johannes Gutenberg was involved in the development of the movable type printing press [2].
The Wikipedia page on the 15th century is [3].