Thank you Wagner,
Unfortunately I am missing something (seems like JWT InsufficientPermissions error - #4 by wlandgraf)
(For now) I narrowed it down to:
The API Server has JWT as middleware installed with the correct (symmetrical) key
The API has set all DefaultEntitySetPermissions
My Entity ahs the attribute [EntityAuthorize(EntitySetPermissionAll)]
When I access the entity without a key (also in swagger): I can access the all methods for the entity
I clearly am missing something trivial…
Thank you