I wish each blog was still maintaining a blogroll. I have found many interesting websites by looking at what people that I like to read are subscribing to themselves.
Another dying approach is a planet. Planet Python is double cool, because not only it aggregates to Python related blogs, but also links to other planets!
Does the owner of this site notify blogs that they’re included and give them an option to opt-out?
Why would they? If you make your blog public, for everyone to read, then other people can talk about it. And categorize it. And link to it. That is basically how the internet works.
They are selling their dataset, which might rub some folks the wrong way (without an opt-out) https://blogsurf.io/data
That is actually quite a neat way to monitize a site like this. No problem with manually adding 30 feeds, or pay 5 to get the opml file… Clever