Thanks for your reply. I made the changes as you suggested, but I still get the “Please wait…” page. Here’s my conf file for reference:
<VirtualHost *:80>
        ServerName beatmap.pmeal.com
        RewriteEngine On
        RewriteCond %{HTTP:Upgrade} =websocket
        RewriteRule /(.) ws://localhost:8501/$1 [P]
        RewriteCond %{HTTP:Upgrade} !=websocket
        RewriteRule /(.*) http://localhost:8501/$1 [P]
        ProxyPassReverse / http://localhost:8501
</VirtualHost>

I also added the config.toml like you suggested.