I would advise using Nginx infront of it.
You can google NodeBB Nginx Config and you'll have one you can copy/paste.
Nginx will then be on port 80 and you can close 4567 on your FW.
I want to change my URL of the forum, but it seems to me that the only place we can set it is when setuping it. I am concerning whether the data will be removed when re-setup the forum. Is there any other method?
./nodebb setup (or
node app.js --setup) doesn't change any data (at most adds an admin if no one has been added yet). you can safe run it to reconfigure your board
Btw: welcome to the NodeBB community