I mostly use it for news, but a lot of sites have RSS even some that do not advertise it.

Whenever I like a site I usually use rss validator and check if their blog/news page have RSS.

Additionally I check endpoints like /rss and /feed.

Not the most concrete answer, but what you subscribe to is highly personal.

P.S. I also use something like https://ktnrs.com/ for websites providing only email newsletter.