Small world - I'm currently cleaning up scans of the EB 9th edition to put it online as a mediawiki site; I'm including all the illustrations and plates so I'm only a third of the way through.
I've been testing different OCR tools and so far I've been the most impressed with paddleOCR - it correctly split the text columns, labled the illustrations, and noted the maragin text.
Still, it's not perfect, so I'm having to hand-edit some tables. I plan to put the source pages online as well so you can switch between the scanned page and the electronic text.
I'm looking forward to it. The 9th is great in its own right and a lot of it is in the 11th. Alfred Newton's nearly 200 articles on bird species and a few classic essays by Macaulay come to mind offhand.
For those unfamiliar, the 1875 9th ed. was known as the scholar's edition due to how many eminent persons had contributed; it's a fascinating snapshot of the late 1800s.
Other material that would be fun to put online in a hyperlinked and indexed format include geographic and medical atlases and the Baedeker travel guides.