Obviously checkout links aren't valid submissions here, and you should flag them so we can kill them and perhaps ban the sites.

Paywalled articles are different. That's a settled matter on HN. The rule is that paywalled articles are ok when there's a workaround:

https://news.ycombinator.com/newsfaq.html

https://news.ycombinator.com/item?id=10178989

Yes, the paywalls suck, but it would suck worse to deprive HN of the better NYT, WSJ, Economist, New Yorker, etc., articles.