Do I have to subscribe to read this content?
No, you do not have to subscribe.
Underneath the button “Subscribe”, there will be some text of smaller size written.
To access the article, you can click “read this article for € X” which allows you to purchase only the article.
You will have infinite access to the article, since you purchased it. This is sustained as long as the platform you purchased it from does not delete the article nor shuts down their website.