Finally, to make a summary, I met a strange problem when building nodebb: when I write a post, the uploaded pictures can be displayed normally, but the picture links cannot be displayed.
The solution is to set "cross origin embed policy" to the state shown in the following figure:
屏幕截图 2022-01-26 153145.png
However, there is another strange problem. When you use "www.domain. Org" to access, you can display pictures normally, but when you use "domain. org", you still can't display pictures.
You can configure nginx to make "domain. org" jump to "www.domain. Org" through 301。
Welcome to my station, ahoh.club，Thank nodebb, thank Mr. cat(baris).