The feed url can be the same & that will keep working fine but it's the cotents within that can & will change with time. Ideally a feed should offer HTTP urls if it's from a HTTP feed & HTTPS from a HTTPS feed url but there's a general shift to just providing HTTPS urls irrespective as most clients support it.
Playing the feed entries as a stream is going to always fail with HTTPS urls as the solution that in_mp3 (the MP3 decoder & stream handling plug-in) uses doesn't cope correctly with HTTPS & so it'll fail. Nothing you're doing wrong, just the age of that (annoyingly) important plug-in means it's less compatible with the modern age than would be liked.
Anyhoo, I've added the HTTPS -> HTTP change to the todo list as it shouldn't be too much of an issue to get it done.
-dro
