But if someone accesses my server by IP address
As far as I know, it chooses the first server that is in your generated config. That order likely matches your config.xml file. There is no control in the UI.
QuoteBut if someone accesses my server by IP addressyou can also add server with your ip in server_name
difficult due to dynamic IP on my home set-up
You can use dynamic dns providers if you like to make it easier to call it anyway.
The default_server option has been implemented in 21.7.7.