There are 2 functions :

1. Backing up all you notes, data, mp3’s and so on

2. Publishing as a RSS feed for podcasts

Re. (1): In the spirit of Nostr , that is something client software should provide, and just save all your notes and stuff on a local disk.

Once you have that, you can use the RSS feed of choice, if they cancel you or go broke, just switch to another feed.

AdamCurry@ , the inventor of podcasting, has started PodcastIndex.org , that vows to never drop a single episode from all listed podcasts. Take a look!