Following & Notifications - RSS
The easiest way to follow a topic and get notifications is to
subscribe to the RSS feed available for each topic.
RSS is a web syndication technology from the last century, very simple
and efficient. You can find more informations about it here :
https://en.wikipedia.org/wiki/RSS and there :
https://www.wired.com/story/rss-readers-feedly-inoreader-old-reader/