What podcast client do you use? Every podcast in the iTunes directory has a public RSS feed. If you're having trouble figuring out the feed from that directory, you can use a tool to show you the link from the podcast's directory page. For example, paste Smartless' page https://podcasts.apple.com/us/podcast/smartless/id1521578868
into https://www.labnol.org/podcast/
to get https://rss.art19.com/smartless
At this point, just about the only podcasts that don't have public RSS cost money, now that Spotify has abandoned its exclusives strategy. If you were subscribed to a public feed that moved to Spotify exclusive, it's probably started repopulating in the last year.
If you are referring to YouTube shows, all Youtube channels have RSS feeds in the format https://www.youtube.com/feeds/videos.xml?channel_id=UCX6OQ3D... (UCX... is a channel ID.)