Function signature is confused
Deriving a class like
public class ColliderCallback : SerializableCallback<Collider, bool> {}
and exposing it the proper way: public ColliderCallback colliderCallback;
will make it fail to show a function like
bool CallThis<Collider>() { .. }
in the list of available functions in the inspector.
Instead it will show a function
bool CallThat<bool>() { .. }
(if declared).
The included package should be loaded in a new Unity project SerializableCallback_bug_reproduction.zip
I'm not sure that SC supports generic methods at all. It's designed to show only bool Method(Collider collider) as dynamic, and bool Method() as static.
Ill check for options but I can't make any promises.