I ran into the same problem while building https://learnawesome.org/ . Forget the broad class of "learning resources", even the "books" category doesn't have a usable unique ID. Not everything gets an ISBN for example. There's also the ambiguity between a "work" and an "edition" of a work.

This is probably why OpenLibrary supports mapping of books with 40+ identifiers: https://github.com/internetarchive/openlibrary/blob/master/o...