Install comment_notify module to have an easy solution to subscribe/unsubscribe to nodes like a forum topic.
Installation with composer:
Enable with drush:
Configure it under ../admin/config/people/comment_notify.
Select the Bundle on that you want to enable it. Chose "All Comments" under availible subscription modes and set it as default state.
Issue:
You want to get informed about updates on nodes like forum topics and need an easy solution to subscribe to it.
Solution:
During research we found the comment_notify module.
Conclusion:
Install the module, enable it, configure it. Thats it.