Gallica (https://gallica.bnf.fr) is the French National Library's website for facsimiles of books, newspapers (and other stuff as well).
Most of the documents there are in the public domain, though sometimes it's not the case.
Gallica also implements IIIF, if needs be to download high-quality images of individual pages (maybe for djvu?), however it enforces quite strict rate-limits on the endpoint.