It looks like there’s several distinct components to gpodder which confuse things.

Firstly gpodder seems to be a desktop podcast client.

Secondly there’s the sync service / protocol. Gpodder.net provides this for free but according to antennapod doesn’t have adequate resources and causes errors in your client (which I can confirm). There are other containers available which are not from the gpodder team but emulate the protocol.

Finally there’s the recommendation / discovery service apparently provided by gpodder.net. I haven’t been able to get this to work because my client hasn’t been able to sync yet, despite 12 hours of trying.

In my own case, I already have a client (antennapod) and I’m not really interested in sync because I only use the one device. The recommendation / discovery service would’ve been cool but it seems broken for the moment.