There is a nice (but introductory) discussion of the Is-Ought distinction at Prawfs, with contributions from Jeff Lipshaw & Rick Hills. For a slightly deeper discussion, see Legal Theory Lexicon 014: Fact and Value. And here are four relevant entries from the Stanford Encyclopedia of Philosophy: Rachel Cohon, Hume’s Moral Philosphy, Richard Joyce, Moral Anti-Realism, Michael Ridge, Moral Non-Naturalism, & Mark van Roojen, Cognitivism vs. Non-Cognitivism.
All the theory that fits.