I thought this was cool because it worked even in my old browser. So cool I went to add their RSS feed to my feed reader. But then my feed reader got blocked by the system. So now it doesn't seem so cool.

If the site author reads this: make an exception for https://www.owl.is/blogg/index.xml

This is a common mistake and the author is in good company. Science.org once blocked all of their hosted blogs' feeds for 3 months when they deployed a default cloudflare setup across all their sites.