Also I'm using VPS to proxy like:
https://i.ibb.co/1bjh0sR/Screenshot-2024-04-30-at-14-48-07.png
I need to know how to configure reverse-proxy at PROXY VPS (like fowards the IP?)
And How to install flarum and configure it to work with reverse-proxy(like listen fowarded IP?)

Sorry I'm really bad at this,
please help me.

I'm plan to install Flarum to Origin(check the attached img)
And the VPS PROXY will just proxy/fallback server. (I'd like to hide my origin so)

I don't know if we can help. Installing flarum is another question than configuring a complex reverse proxy. You could use Stackexchange to ask the question related to your setup, then install Flarum once up and running.

I'd like to know Does Flarum support reverse-proxy.
And I failed to install Flarum before (admin page, e.g. are somehow 404)
So I'll try reinstall but... idk

    d1hydr0gen Flarum should work on any environment. A reverse proxy isn't any different. As long as the requested url matches the url value in the config.php everything should be fine.

    It's been a while that I worked with a reverse proxy though.

      I see, thanks you.
      For other question, Is custom SMTP supported to send verification email?
      And Is Cloudflare Turnstile supported? For preventing from spams.