Doesn't support prefabs?
I have a prefab that uses BetterEvents. I can edit said prefab from the Projects window with no problems whatsoever, but, If I put an instance of the prefab in my scene and open its inspector, I get this:

Is this a bug, intended behavior, or am I doing something wrong?
Odin Inspector does not support unity prefabs. That is one of the major flaws of using Odin in my experience. It comes with a great tool set that amplifies overall workflow, but it also comes with some costs, Unity Prefabs is one of those costs.
It's not that it doesn't support prefabs at all, just seems to have some issues with it. I've had the same message but can use BetterEvents fine now within a prefab (using SerializedMonoBehaviour and [OdinSerialize] attributes)