Personally, I’m using Pocket Casts, but you can’t use it on desktop without their premium subscription, which I don’t need. Antennapod is a good Android App and supports sync through gpodder.net, but there are no good iOS apps supporting gpodder, so I stopped using it. But I thought you don’t need Spotify Premium to listen to podcasts on there. It might be easiest for you to just keep using it for that.
Are you sure NextPod can’t play the episodes? Because it lists it as a feature on their github https://github.com/pbek/nextcloud-nextpod
That’s the thing. They don’t make their camera app available to third party ROMs despite officially cooperating with one, and they also haven’t made the camera’s features available to third party camera apps. So for me, being on CalyxOS myself, that announcement email read like a joke.