You should read about OPML blogrolls [1], they are gaining traction in this space. Personally, I like the idea of manually exploring recommendations, so I built a browsable index [2]. But you can crawl the these as well and build all sorts of recommendations engines.

[1] https://opml.org/blogroll.opml

[2] https://alexsci.com/rss-blogroll-network/discover/feed-c550c...