Trying to save any generic type using wildcard type (Java's ? extends X or ? super X and Kotlin's out X and in X) currently creates a FieldTypeError.
Java reflect stl represents them using instances of WildcardType.

So the issue is that it crashes, not that you want to (de)serialize wildcard types? I suppose wildcards could be done with @Dyn (sorry to whoever @DYN is for the ping) as I don't believe it requires a serializer outside of the dynamic ones, but if anything tried to grab a wildcard serializer it would immediately fail to and crash.

In my specific use case the generic type is a final class, but in a kt List (which has out variance), however it could be useful to support dynamic for it.

I could make it serialize as the bound, or I think you could use @JvmSuppressWildcards