Over in this ticket from 2017, Glyn asked to allow the UI httpd port be user-configurable to something other than the then-hardcoded 80.
Later in the comments, Chris said: "Once [WiFi] 3.x supports HTTPS changing the default secure port 443 to another port would not be a problem."
Jeremy later said, "The ESP32 build will have support for the server to run over HTTPS, that is what Chris means by it will be supported in the 3.x version"
I've just replaced my 2017-vintage ESP8266 WiFi module with a freshly-flashed Huzzah ESP32-WROOM-32, loaded with v4.1.2 . A bit off googling didn't point me to anybody stating how they've changed either the UI's port number, or to enable https (on any port).
The issues can be tracked here. We are currently working on an overhaul of the Networking subcomponents to enable these improvements, in addition to many more.
Thanks. I've now subscribed to those.