• https://getrssfeed.com - extract RSS feed from Apple, Spotify, Deezer, Soundcloud links
• https://www.labnol.org/podcast - give it an Apple Podcast URL and it returns the RSS feed (web form)
• https://fetchrss.com/generator/init - self-blocked behind captcha

Soundcloud

Is the podcast you want to listen to hosted on Soundcloud? First of all, double-check that the podcast is not also hosted somewhere else (more often than not that is the case, and then you can simply avoid Soundcloud).
Soundcloud makes it really hard to discover the podcast's RSS feed. It is not shown anywhere on the page, nor in the HTML source.
Based on a feed URL we already possess and that channel's Soundcloud landing page, we can manually construct the hidden RSS feed endpoint for any Soundcloud "podcast":

1. Open the HTML source of the Soundcloud "podcast", for example https://soundcloud.com/user-268302561.
2. In the HTML source, find the user ID property, which looks like soundcloud://users:819898639 (I suggest grep for soundcloud://users).
3. Copy the numeric part, and construct a URL like this: https://feeds.soundcloud.com/users/soundcloud:users:819898639/sounds.rss.
4. Take a moment to reflect on the awfulness of siloed web services and do your best to avoid encouraging them in future.