If other things don’t pan out, you could see if the Mankato Maker Space wants it. I’m not really involved, but I’d make the drive for them if they do.

Most things people self host are either torrent clients, HTTP(s) or are game servers. The first one can pick a port arbitrarily. The second can do host routing. The third - some of them support SRV records so you can direct the client to an arbitrary port. It’s becoming less common to need multiple public IPv4 addresses.