Ah, I did indeed misinterpret you. On further investigation, I have found one authority that works in xdg-open: localhost. Not the host name, not 127.0.0.1, no

Ah, I did indeed misinterpret you. On further investigation, I have found one authority that works in xdg-open: localhost. Not the host name, not 127.0.0.1, not ::1 or [::1], not anything else present in /etc/hosts, just localhost. I’m baffled, but not quite invested enough to delve into the source to figure out what could be going on.