This sounds cool: The DECRYPT Project
Includes history and AI/ML tools.
https://de-crypt.org/
About:
Thousands of enciphered historical manuscripts are buried in libraries and archives. Examples of such material are diplomatic correspondence and intelligence reports, private letters and diaries as well as manuscripts related to secret societies. The bulk of these historical manuscripts will remain undeciphered unless we can automate the processes involved in decoding them. Our aim is to develop resources and computer-aided tools for decoding of historical source material by using AI and cross-disciplinary research...
Tools:
collection of digitized images of ciphertexts and encryption keys along with metadata information about their provenance, location, transcription, and possible cryptanalysis or commentary.
all records in thedatabase are open to the public
tools for transcription and decipherment of historical ciphers
Historical cipher images can be transcribed, i.e. transformed into a computer readable text format
transcribed ciphertext can be corrected
Decode Database, HistCorp, TranscripTool, CrypTool whatnot.
open source under the Apache license v.2.0 with the exception od Decode db.
Quite a few Hungarians in the project apparently. They started publications in 2019 so fairly new thing this is, probably the emergence of these machine learning models allowed them to form this team.

Looking at the Decode db, the earliest dated document is from the 15th century. There is one that says 1300-1699. I think accessing documents needs a registration, at least when I tried to enlarge the photo of the document it said I have insufficient permissions.