Running Ignition doesn’t prohibit you from running other web servers like Apache, IIS, nginx, … Ignition only needs one port, you can run those other services on a different port.
There’s even a hack where you can use the built-in web server to host additional static content: [Question] Loading images from gateway's file system Though, as far as I know, it’s not officially supported, so may be removed without notice in future releases (presumably only when they will change technologies, in which case you can still install a third-party server).