Right! I was curious about how they do it and found out that Youtube actually has RSS feeds! At least according to this and a few other pages I've found https://danielmiessler.com/blog/rss-feed-youtube-channel/

Also, I can see that for other services like Twitter, there are indeed third party providers that can create feeds https://rss.app/blog/how-to-create-twitter-rss-feeds

Also Reddit subreddits and users: https://www.reddit.com/wiki/rss

For podcasts, just don't use Spotify and instead get the RSS feed of the podcast you like

So, yeah I'm now thinking of going to my RSS reader (which I currently only use for news) and adding all sorts of stuff.

Thank you for posting your comment :-)