I wrote a plugin that makes updating this list easier. We used to update the OP when people posted new urls but it was time consuming and urls that no longer worked just stayed there forever.
From now on if you want to submit your NodeBB forum you can do so at https://community.nodebb.org/who-is-using-nodebb/submit, before you submit make sure your NodeBB is running and publicly accessible. I also pull some additional data like description and keywords so make sure you set those in your ACP. Starting 4.0.3(which this forum is running) it will also pull the brand:logo set in the ACP.
The table in the main post of this topic is updated dynamically from the submitted urls. If a forum is not accessible it will not show up. A cronjob checks the submitted urls every 6 hours to keep the list updated.
If you want to see a nicer view with all the information (description, tags, logo) you can visit https://community.nodebb.org/who-is-using-nodebb, since only this forum is running 4.0.3, it shows a logo but as more forums update it will show up there too.
I updated the list from some of the forums from the original list, if you don't see yours please feel free to submit it from the submit page.