[A2A] Fun exercise.
In biblical (Old Testament) times, the Canaanite alphabet was common to all Canaanite nations—from Moab and Edom in the southeast to Phoenicia in the northwest. The language was substantially the same, as well, throughout that period, with dialectal differences that widened over the centuries, so that by the time of the late First Temple period (750–580 BCE) mutual comprehension was only partial.
There are plenty of references to letter frequency in modern Hebrew (one good English-language one is Stefan Trost’s Character Frequency: Hebrew). However, although linguistically modern Hebrew is very similar to biblical Hebrew, it does contain many words of foreign origin, and tends to use ‘full spelling’ (i.e. use the letters vav and yod to indicate the vowels /o/u/ and /i/, respectively), which can skew the results somewhat.
So a better test would be a certified ancient text of sufficient length to be indicative.