Values of a Space-Faring Civilization

Most discussion in longtermism centers around preserving humanity's future, but it is also important that we think about what humanity's future should look like. For example, assuming we develop into a Type III civilization, what should our values and priorities be such that we make the best possible society in a galactic context? I haven't seen any discussion of these questions, the closest I've seen is people talking about value lock-in as an existential threat.

Does anyone know if there are any books or post series on the topic? I'm considering writing a book on it myself, and I'm curious how neglected it is/how much work has already been done.