AntennaPod promotes a non-free network service and contacts it before seeking user consent
When a user first starts AntennaPod, it immediately contacts Apple servers to get recommendations from the iTunes API.
I was told that this behaviour can be switched off by choosing the “hide” region in the upper right corner of the discovery screen. However, by this time, the damage will already be done. This should be an opt-in feature, or the feature must be removed for the app to be GDPR compliant.
Issues about this were closed as wontfix by the developers: