Rockabetty

Apple Podcasts: Open the app, tap Library, then tap the three dots in the top right corner, Follow a show by URL, Paste the RSS feed URL and tap Follow.

Spotify: Spotify doesn't support custom RSS feeds directly. Try Pocket Casts or another app.

Pocket Casts: Tap Search, then tap "Submit RSS feed" at the bottom. Paste the URL and tap Subscribe.

Overcast: Tap Add Podcast, then paste the RSS feed URL and tap Add.

Google Podcasts: Tap your profile icon, then Activity > Subscriptions > three dots > Add by RSS feed.