nmcheck.gnome.org doesn't work for NetworkManager connectivity check
https://gitlab.gnome.org/GNOME/gnome-shell/-/blob/main/js/portalHelper/main.js references nmcheck.gnome.org
I visited http://nmcheck.gnome.org/ in a web browser. It returns a basic 404 page with HTTP status 404. According to the NetworkManager documentation, a connectivity check page should return either the special text "NetworkManager is online" or it can do like Ubuntu and return HTTP status code 204 with the header X-NetworkManager-Status: online
.
(Fedora uses the special text "OK" but this requires adding an additional line to the NetworkManager conf files to override the response.)
Because it doesn't return the correct text or header, it's not possible for this URI to be used by NetworkManager's connectivity check. I think nmcheck.gnome.org should be configured so that it can be used by NetworkManager's connectivity check.