Application Composer Custom Object Object Functions Return Type Limited to String for External Apps

Summary:

From the "Server Side Scripts" of a custom object I want to create an "Object Function" that returns an Object (Json Object preferrably) or a Map and that has the Visibility property set to "Callable by External Systems".

Unfourtunately the POST call that returns the function output is only exposed when the "Returns" value is string.

Is that a limitation of externally callable Object Functions or is there any solution or workaround that I did not test.

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