nginx/pages.conf

server {
    listen 443 ssl http2;
    listen [::]:443 ssl http2;
    server_name ~^(?<user>.+)\.exozy\.me;

    include conf.d/ssl;

    root /srv/http/pages/$user;
    index index.html;

    error_page 404 /404.html;
    location = /404.html {
        internal;
    }

    location / {
        try_files $uri $uri.html $uri/ =404;
    }
}