I am not sure if there is a good way to do it without scripting, and a router that would allow for taking variable input from an external script. But theoretically if the router would support it, you could script a port change at times there are no one on the server.
Essentially the server port is in a text file, you could use some command line utilities, and write a script leveraging something like sed to change the port in place.
But I am overcomplicating it. lol
I ditched reddit, and what’s being described in this thread is largely part if why I left. I won’t go back.